Australia is not isolated from the rest of the world, and, politically, economically, socially and culturally, is very affected by what is happening beyond our shores. But middle power, or not, whatever that means, Australia's capacity to affect events abroad, in any sort of way proportionate to the way they affect us, is very limited. Generally it is in inversely proportional to how far an overseas capital is from ours. We have a certain amount of clout in Wellington, Port Moresby and Dili, a very good deal less in Jakarta, and not much at all, when it really matters, in New Delhi, Beijing, and Tokyo.

One can rarely judge the quality of a relationship on common interests, mutual backslappings and assiduous exchanges of birthday cards. It is about what happens when we disagree. Paul Keating, among others, once remarked that your real friends are those who stand alongside you when you are wrong, not those gathered about when you are right.

Our leaders judge, possibly rightly, that being seen as a reliable and steady ally of the United States, and joining it in its adventures because we are an ally, is the strategy most likely to keep potential enemies at bay. This is whether we see the problem similarly, or agree with the proposed solution, or not. We rarely test the relationship by sharp disagreements about realities, aims and intentions, or doubts, publicly or privately expressed. Our focus, often, has been to anticipate the tough decision likely to be made, and to be seen to be calling for it first.

Only rarely are we seen or heard, here or abroad, counselling discretion. Occasionally, as recently over the shooting down of flight MH17 in the Ukraine, we have taken a lead role on behalf of the West, but when that has happened, it is usually for our capacity to say things that might seem less credible coming directly from, say, the US, Germany or Britain.

There are upsides as well as downsides to behaving as if we were a dag hanging off the American sheep. It sometimes annoys the neighbours, or our trading partners, particularly China. But it creates an impression of access to American power and thinking. This can work well in domestic policy terms. Others can only guess if we can draw on our loyalty points if we are in trouble.

Yet for more than 70 years, Australia and Australians have struggled to be noticed panting alongside the sheep, whether by those watching the sheep, or the sheep itself. Most American histories of World War II make only the most cursory reference to Australian participation, other than to make clear that none of those sometimes referred to as Allied troops were involved in any of the important decision-making. Diplomatic and political histories of the past sometimes make clear how much our foreign minister of the day, Bert Evatt, was loathed and distrusted in Washington and London, in part for demanding that Australia be accepted as an independent nation deserving some consultation.

Australia, its leaders, and military actions in concert with America, get a token index mention or two, but nothing suggesting that we ever made the slightest difference, except sometimes as ballast for the claim that American actions were with allies.

If from time to time we disagreed (say when Gough Whitlam loudly criticised US bombing of North Vietnam) there might be a Nixonian paragraph dismissing such frank and friendly intercourse as treachery, and emphasising our unimportance in the scheme of things. US histories of its adventures in Vietnam, the Gulf Wars and Afghanistan rarely mention Australian activities - even more rarely any Australian military or political contribution to the grand strategies or tactics. Perhaps we should be thankful that most of the world, even the Muslim world, has had no idea we were there.

Australia will be briefly at centre stage when we host the annual G20 conference in Brisbane in a fortnight's time. Major world leaders are coming. That's nice but no big compliment The last five G20s were, in order, in Pittsburgh, Toronto, Seoul, Cannes and Los Cabos. No one attaches any particular significance to what happened, if they remember, to the location or the host state, or its prime minister. But Australia has some capacity to influence the agenda, as well as some capacity to bask in the presence of so many world leaders looking in awe at Tony Abbott.

Traditionally G20 meetings have been focused on economic policy rather than security. The economies of Europe and the US are faltering, and some are in serious trouble. Japan is going backwards. People are unsure whether China is in control of its economy. Others , including Australia, are battling along, but, in many cases, the capacity of their governments, or their central banks, to keep the ships steady is in clear decline. Nor is it clear that the slogan-based austerity preached by Abbott at the last G20 contains magic medicine. Or that Australia's own economic management, since the Coalition rescued us, is any rostrum from which we can hector others about discipline, courage and adherence to principle. No one is coming to learn from us.

Six matters, not counting global warming, which we don't want mentioned, could "distract" world leaders.

There's the threat of the spread of Ebola, which had finally reached a point going beyond pious expressions of concern about something far away into a realisation that an epidemic extending beyond Africa could be a serious challenge, even to economies.

There's the crisis in Ukraine, not only for itself but as a symbol of increasing tensions between Russia and Europe, fears of dependence on Russian energy, and of an angry, increasingly nationalistic and possibly expansive Russia. Alongside, but separately, is the backlash against Russia for the shooting down of Flight MH17. Australia and the Netherlands have taken centre stage as spokesmen for the victim nations, and Abbott has publicly threatened to "shirt-front" Russia's leader, Vladimir Putin, over the affair in Brisbane. The Russian response was hardly conciliatory, and many will be disappointed if there is not a vigorous confrontation. On one hand Abbott could hardly lose (domestically) by being publicly angry; on the other he could be humiliated (internationally) when Russia takes the opportunity to spell out how little it cares about us.

There's the sudden upsurge in domestic terrorism, whether about lone wolf incidents, such as in Australia, Canada and the US, or the fear of a team outrage such as at Bali or in the Madrid or British train systems. Most Western countries have considerably increased internal security and toughened the surveillance, detention and interrogation powers of their security agencies. Brisbane itself will be an example of that, with all of the risk that this will in itself provide a temptation.

Fresh jihadist terrorism is in part a function of the rise of the Islamic State movement, including its apparent taking from the al Qaeda movement the mantle of lead player in a war against western hedonism, Christianity and "occupation" of Muslim countries. IS now controls substantial territory in Syria and Iraq, and provides (in a much more efficient form) all of the trappings of organised government, from garbage to police, health and school services. IS has proclaimed a caliphate in terms that suggest, in effect, a renewal of active war to conquer the world for Islam. But that includes an incidental, and perhaps more urgent, intention to resolve once and for all, the great schism in Islam, between Sunni and Shia, which began with the death of Mohammed in 632, the fight over the succession and the proclamation of the first caliphate.

The militant belligerency (and malignancy) of IS, and, perhaps, its apocalyptic vision and dream of martyrdom, has galvanised young pious and fundamentalist Muslims, whether in Muslim countries or in Western nations where Muslim people are in a minority. The problem is not common alienation, or mere existential angst; it is that IS is inspiring thousands, including from Australia, with a vision of making a difference, in a cause that matters. That the cause is mad, and that its leaders have hijacked the train, is neither here nor there compared with the sense of mission and certainty imparted. Most Muslims disapprove of IS, but many take some pleasure at its success.

Be all of that as it may, the rise of IS is but a part only of pressing local problems where it operates. Even before IS existed, Syria was in civil war. Next door, Iraq was falling apart because of corruption and because its government had become an instrument by which the Shia majority was persecuting the substantial Sunni minority, including with a restoration of tribal politics, strongmen, and armed gangs, or militias. The success of IS, in both Syria and Iraq, is in part a function of its ruthless extermination of rival Sunni gangs, including the local outpost of al Qaeda, with a somewhat more moderate view of the world. For many Sunni folk in Syria and Iraq, life under IS, if tough, is preferable to routine rape and pillage by Shia gangs, including the formal armies of the government whom we are now trying to train and civilise.

Busily manipulating the situation, in their own interests, are all of the neighbouring countries. Turkey, a secular (but essentially Sunni) nation, can hardly decide who it hates most: the Syrian government; the Syrian government's most effective enemy (IS); or Kurds, most of whom have been violently involved in efforts to create an independent (and anti-Turkish) nation out of Kurdish sections of Turkey, Syria, Iraq and Iran.

On the whole, the Turks have disliked IS least and have actively facilitated the passage of IS volunteers across Turkey. In recent weeks, Turkey has been pressured by the US, to permit a limited number of Iraqi (but not Turkish) Kurds to cross its borders to give limited, and probably not decisive help to Syrian Kurds..

Shiite Iran is actively manipulating the tension in the hope of extending its reach. It has had enormous influence over the Iraqi government, and Australian soldiers will soon be in (advisory) action alongside Iranian soldiers in Iraq. Iran is also a player in the fate of the Syrian government.

Sunni Saudi Arabia has long been playing a double game, and at best, from the Western points of view, seems to hope that the last IS warrior kills the last Shia one. Otherwise it would prefer that IS won if the alternative were confessional Shia neighbours. Meanwhile, it, and some other Sunni Arab regimes, will give token support to the West, so long as their contribution does not have to extend to putting any of theirs at risk. In exchange for all of this help, Western countries are according to their Arab "allies" the title of the moral leaders of the campaign. Meanwhile, great efforts are going, not all of that successfully, into persuading the new Iraqi government to be "more inclusive", and less beastly to the Sunni, even as IS-dominated coalitions now actively threatening Baghdad. One can expect that a lot of Western bribery will be involved, and not only for our allies in Baghdad.

The problem with all of these "problems" or crises is that none of them are presently under control by any sort of collective of the countries which make up the G20. At best, I suppose, Putin could agree that Abbott was right, and promise to pull out of Ukraine and never to shoot down aircraft again. That's unlikely.

Otherwise a happy and successful showcase of Australia's international citizenship involves hoping and praying that everyone and everything, from the Ebola bug up, behaves for the next fortnight.