The argument against US overseas military bases is almost always a surrogate argument against the exercise of US power. But you can't have one without the other. And the annoying thing about American hyperpuissance is that, compared to other probable outcomes, it produces what appears to be the least bad international system. And so, various allies continue to tolerate, and even encourage, the presence of US military installations in their countries. On 23 July, Iraq's prime minister,

Nouri al-Maliki, took the occasion of his first visit to Washington since the election of Barack Obama to signal that he would rather US troops did not withdraw entirely from Iraq in 2011. "If Iraqi forces required further training and further support," he told an audience at the US Institute for Peace, "we shall examine this at that time based on the needs of Iraq." Indeed, the Iraqi prime minister is more enthusiastic about continued American imperialism than is the US president.

Maliki apparently appreciates the realities of geography better than Obama does. The strategic justification for the Iraq pull-back is that US forces will return to their previous posture as "offshore balancers", relying on naval and air strength to tip the balance of power in the greater Middle East. America's allies in east Asia - Japan in particular, but also Australia, which has just produced a defence white paper suggesting a need to "hedge" against the ebbing of US presence in the western Pacific - are experiencing Maliki-like anxieties. For those people who feel themselves most exposed in a dangerous world, the proximity of US forces is apparently comforting.

To be sure, the US military presence is not a free good for these countries. Again, Maliki's very delicate domestic political calculations are illustrative: the line between "occupier" and "strategic partner" is a fine one, but nowhere more so than in Iraq. Nor, from an American standpoint, is having to work with leaders such as Maliki a perfect blessing; through the years the US has made alliances of convenience with some very nasty people.

But that there should be a liberal purpose to statecraft is a rather uniquely Anglo-American, almost Whiggish idea. What is historically distinct about US power is that it correlates quite remarkably with the spread of human liberty and representative government, through time and across cultures. What has been true abroad has also been true at home: the cold war period, so far from producing the feared "garrison state", also brought a dramatic expansion of political rights for African Americans, women and even homosexuals.

And so two cheers for the global exercise of American power and the overseas military bases that are a necessary consequence thereof. Given that lamentably few governments in human history deserve any applause, one can see why not only Americans, but many others around the world think the risks are worth the reward.

Thomas Donnelly is the director of the Centre for Defence Studies at the American Enterprise Institute