Gideon Rachman, the FT’s chief foreign affairs columnist, says “the challenge for the US now will be to avoid sliding straight from imperialism to isolationism”. The imperial idea became fashionable in 2003, he notes, when it was driven by the likes of Dick Cheney and other conservatives. It has declined in popularity since.

Imperial analogies still fascinate America. But the latest American books on empire are markedly less optimistic than the ones appearing a couple of years ago. Cullen Murphy’s Are We Rome? – which made the best-seller lists this year – argues that the US is in danger of emulating Rome’s decline and fall by succumbing to Roman-style corruption and arrogance. America needs to rediscover its civic virtues.

Rome is the empire to which most parallels are drawn, which is a fair enough point when you consider how much Roman imagery and ideas have been incorporated into American institutions. Rome, however, did not fall because of “corruption and arrogance”, though these did play a role in its decline. Economic mismanagement and rampant inflation were major contributors to the empire’s collapse — and these are lessons from which the US (and other world powers) can learn.

The conservatives who embraced the word “empire” a few years ago were being deliberately provocative. If America was indeed in something like an “imperial” mood in 2003, it simply meant the US was determined to use its economic and military pre-eminence to change the world. If that involved invading, occupying and reshaping whole countries, so be it.

Four years on, “imperialism” looks a lot harder and less attractive. America’s generals fret publicly that their formidable military machine could be “broken” in Iraq. The fiscal deficit is mounting and the dollar is falling.

However, Rachman points to a future for Amercia’s global position — because it is so tied to the world’s economic well-being.

China, India and even a resurgent Russia are emulating America by trading their way to greatness. Their ruling elites are directly enriched by globalisation.

I wonder if the story will change in 10 or 15 years’ time. Will China have overcome most of its internal problems and truly emerged as a world power? Will India be hot on its heels? Or will the impending climate catastrophe lead to an entirely different world order?