Turnbull reproved Shorten this week for describing Trump as "barking mad". This is arguably true. One should think that Turnbull, like many others on the conservative side of politics, thinks much the same, as does (at least according to Shorten) John Howard. When Turnbull reproved Shorten for saying what he did, he was not criticising him for thinking it, but for saying it. Such remarks won't help Australia if Shorten, at some future time, is representing our interests. The more so given that Trump has a notoriously thin skin, and would bear a grudge, against this nation as much as against Shorten. And how horrible to imagine his taking it out on our ambassador in Washington, Joe Hockey.

But it is to be hoped that the tiny stoush does not serve as a warning-off on discussion of foreign affairs or defence, or the American presidential election over the next month.

The election of Hillary Clinton might make no great difference to a fairly bipartisan Australian foreign policy. But the election of Trump has the capacity to make more difference to Australia's position in the world than almost anything the new Australian government could do over the coming months. A Trump presidency could fundamentally change our alliance position. Trump has been making all sorts of belligerent noises about raising a tariff wall against Chinese imports and forcing trade negotiations that would swiftly improve the US's now lopsided balance of payments with China. One way or another, that has the capacity to slaughter our trade with China. If Trump means what he says about a return to US protectionism, our growth and jobs will be greatly affected. And ever so incidental is a greatly increased risk that an already tense military stand-off between China and the US could lead to armed conflict.

Australia's capacity to affect such outcomes might be limited, particularly if we follow, as we usually do, a line that is fairly uncritical of the US, and presume that, if it comes to shooting, we are on America's side.

Our efforts could be devoted to helping Clinton or, at the least, making clear to Trump, or American voters generally, the risks to us and the US from his belligerent talk to American constituencies. Other nations, including Germany and Britain, have already tried, even if, one suspects, that increases Trump's popularity.

Well before that, Australian politicians should be doing more to explain to voters just how easily things could change overnight, and how "plans" and "jobs" – on whatever side of the political divide – could come quickly unstuck because of the effect of a Trump election on our trading position and our dollar.

The damnable thing is that some of the risks to Australia could be greater during the uncertainty between the Australian election date in July and the US election date four months later. The president will not take office until January 2017, and, after the result is known, nations and others will have at least some time to judge where their interests lie and calculate their responses. Over the next five months, however, traders, treasurers and defence planners must prepare for all contingencies. One may have well-informed opinions about the likely outcomes, but Trump has consistently exceeded expectations of voter support (just as Clinton has consistently failed to meet expectations).

Even without anyone doing anything drastic, the American uncertainties could slow down world trade and economic activity, just as the federal election is doing here. It could lead to pre-emptive actions by trading nations to maintain their positions. It could inspire mischief, including provocations over disputed islands, acts of terrorism or war by players seeking to anticipate events.

Australia might well be a player, and in all sorts of company, in such anxious discussions. One can take it that military, diplomatic, academic and bureaucratic advisers have gamed some of the possibilities and developed lines of advice. We can assume, likewise, that politicians, especially those likely to be sitting in national security and economic councils of government, have opinions and tentative strategies and tactics in mind.

But the Australian public is not in on the secret. It deserves to be. Instead, it is being fed misleading information that suggests that one side or the other has a plan for jobs and growth, able to produce certain outcomes only if that side is elected. Different propositions about tax and spending in different areas are likely —even if nothing much happens — to have only a minimal effect on economic growth. By contrast, the outcome of the November US presidential election affects everyone in the world. Whether in America, Asia, Europe, the Middle East or South America, the guesses nations are making about the temper of the US electorate and the character of one of the bizarre people seeking its endorsement are affecting our lives.

Trump's economic belligerency is not to be seen in his foreign policy pronouncements, even if these fit into his tough-talk pattern. Speeches on foreign relations, such as the one he delivered on April 27, are generally, at least in the hands of would-be statesmen who know the rules, as much at the diplomatic community as they are at the domestic audience.

But Trump is not a conventional politician. Right now he is addressing potential US voters, and he shows very little concern for how his statements are interpreted abroad, or, for that matter, by Americans he does not expect to vote for him. To his constituencies and potential constituencies he is talking about an abrupt shift into protectionism, with tariffs and other barriers to trade, as well as ultimatums to China, in particular restoring the balance of trade. He is a businessman and a person who makes deals, he is telling voters. He will be tough and won't muck around with diplomatic niceties.

It is not unusual, even in this country, to hear politicians talk tough to their own constituents, and rather more winningly abroad, seemingly oblivious of the fact that our trading partners get all of the economic and political intelligence they want. Sometimes, the apparent tough talk on both sides is a charade. But what Trump is talking about and what he says he will do is something altogether different.

At this stage of the American political cycle, a candidate seemingly assured of his party's nomination would be moving towards the centre of politics. The primaries see Republicans appealing to Republican constituencies, especially conservative ones. But the political professions know that they must, at the party convention, prepare an appeal to voters that attracts Democrats and independents, while also galvanising core Republican voters.

Trump's candidature involved war on the organisational party and its mainstream politicians. He mobilised hitherto inactive groups – particularly frustrated, angry and alienated white male voters – and encouraged them to blame all of their problems on immigration, free trade and porous borders. His "war on Washington" message and anger at the failure of ordinary politicians, on both sides, to maintain the standard of living is central to his pitch. Any efforts to reconcile the mainstream, or to appease affronted mainstream politicians, may make him seem to become "just another politician".

Some observers have suggested the Trump campaign is about Trump, not any particular policies. He will say or do anything to get elected. But once there, he may become amazingly conventional, reasonable and anxious, in the ordinary political way, to make deals, compromise and seek consensus. Some campaign positions (for example, on guns, health insurance and abortion) have changed to pander to core Republican opinion, and there is little evidence Trump is attached to them. Perhaps. Trump has been consistently hard to predict, and has continually confounded the commentators.

Shorten is not the first Australian to question a US leader's sanity. (Nor would he be the first to have his own questioned by an American statesman; Roosevelt, for one, thought our Doc Evatt mad.) Richard Nixon was incensed by criticism by Gough Whitlam and his ministers when Nixon resumed bombing of Hanoi in December 1972. Howard attacked Barack Obama when Obama, seeking Democrat nomination for the presidency, criticised America's (and Australia's) war in Iraq. It did Howard no good and, if Obama could not return the insult in person to Howard, he sure did so to Tony Abbott when he came here for the G20 summit in 2015.

It was worse than Mark Latham's 2003 remark about Coalition politicians being in "a conga line of suckholes" to the Bush administration over intervention in Iraq, because the primary insult there was to Australians, not to George W. Bush.

I doubt it will cost Shorten a domestic vote. By my guess, Shorten has about one chance in three of winning the election, and Trump about two in five. Assuming (wrongly) that the events were independent of each other, that puts the chance of president Trump meeting prime minister Shorten in the next three years at about one in eight.

As it happens, Hillary Clinton is saying, as a part of her pitch to US voters, that scores of world leaders are deeply alarmed at the prospect of a Trump presidency (though, to be fair, the Dear Leader of North Korea and the President of Russia have indicated that Trump is a man they could deal with.)

Trump thinks that far too many Western nations are getting their defence on the cheap because of security alliances with the US. He judges this by whether nations are spending 2 per cent of GDP on defence. The bludgers thus include Australia (about 1.8 per cent), most of Europe and Japan. Countries hosting substantial numbers of US troops, including Japan, Korea, Europe generally and Saudi Arabia, should contribute much more towards their security, and, if needs be, develop their own nuclear weapons.

There's a part of Trump that's isolationist, and which wants problems within and between neighbours resolved in the region. Thus, it seems, North Korea is not America's problem but China's. Likewise Syria and probably most of the problems of the old Russian republics, including possibly Ukraine. On the other hand, he promises to bring the war against terrorism right into family homes and, in prosecuting his foreign policy, wants America to be great, respected and feared again. Recent presidents, particularly Obama, have made the US a laughing stock, he says.

Trump has the same fondness for the perpendicular pronoun in discussing his foreign policy as he has in discussing the ills of America, or his own immense wealth. But mostly it is a vision of power in his own hands, and of the combined strength of his personality and might, that will put narrowly conceived American interests first and last.

There are some who claim to see in Trump signs of the totalitarian and narcissistic personality – a vision of fascism, lawlessness and worship of sheer power. A modern Benito Mussolini or Juan Peron. Others think that a good deal of the braggadocio is just that, and that Trump is, at the end of the day, ready to compromise, if somewhat unscrupulous about what he will say or do to achieve the best result he can. They expect he will swiftly reduce his extremist promises – for example, about his immigration wall and anti-Muslim intentions, as well as his sabre-rattling about Chinese trade. But the tough talk has not abated and is the centre of his popularity.

Recent US foreign policy, Trump says, has been a disaster: no vision, purpose, direction or strategy. He is talking of frolics that involved Australia as an enthusiastic partner.

America's resources are overextended. Its military and diplomatic position has been eroded by a weakened economy, including massive debt, low growth, a huge trade deficit and porous borders. Its trade deficit is now approaching $1 trillion a year. (Trump does not add, though surely this must be a consideration in his bluster about China, that the US economy is able to continue only because of Chinese money, invested from its massive trade surplus.)

"To our friends and allies, I say America is going to be strong again ... a reliable friend and ally again ... We are getting out of the nation-building business and instead focusing on creating stability in the world."

China, he says, respects strength, "and by letting them take advantage of us economically, we have lost all of their respect".

More generally, around the world, "I will not hesitate to deploy military force when there is no alternative. But if America fights, it must fight to win ... Our goal is peace and prosperity, not war and destruction."

Australia has spent the past two decades in a generally very profitable triangle in which we have sold raw materials to China, which has manufactured from them to sell particularly to the US. Meanwhile, large sums of money going to the US from Australia in intellectual property payments, services, investment income and profits have helped pay America's interest bills. Australia should be out polishing the vertices. It should be part of our "plan".

Jack Waterford is a former editor of The Canberra Times.