Though America behaved in the 19th century with imperial greed, its expansion was strictly amateur-hour stuff by the standards of the day. It wasn't until the country's arrival as a world power, and its plunge into the Vietnam war, that accusations of imperialism sounded with regularity anywhere outside the Kremlin.
Now, of course, the bug-eyed denunciation of American empire-building is non-stop. So is the publishing of hysterical books on the subject. What a relief, then, to have the erudite, clear-eyed Niall Ferguson weigh in on the subject.
The historian is appalled not by American imperialism, but by how badly it's executed. Before addressing that, though, Ferguson faces the task awaiting any author who tackles the subject: proving that the US is actually interested in empire. Imperial rulers tended to be straightforward about their interest in bringing huge swathes of the world to heel, but the US has an inconvenient way of changing its would-be emperor every four or eight years, and being populated by people who still think fondly of their anti-imperialist forebears.
Authors in the Empire USA cottage industry often present American foreign policy as self-evidently classically imperialist, but Ferguson tries to make the empire designation stick by simply watering down its definition. If an empire can be described as 'a democracy at home, mainly interested in security, providing peace as a public good, ruling mainly through firms and NGOs, promoting a mixed economy, in the interests of all inhabitants, with an assimilative social character', as Ferguson writes, then the parameters don't have to be loosened up much more before we've arrived at the empire of the ham sandwich.
'Central to my argument,' writes Ferguson, 'is that there was such a thing as liberal imperialism (the British Empire, for instance) and that on balance it was a good thing.' He believes that a US version of liberal imperialism 'makes sense today in terms of both American self-interest and altruism', but Ferguson despairs of the country's short attention span.
Venturing abroad and then pulling back without accomplishing much is a recipe for, well, Haiti. This American 'empire in denial' now risks disaster in Iraq and Afghanistan, says Ferguson, because it refuses to behave like a proper liberal imperialist and devote sufficient time and resources to achieve its goals.
But failure in these countries would be localised disasters in faraway places. Ferguson believes the true undoing of America is likely to be internal. As millions of baby-boomers age, the looming cost of the country's health guarantees for retirees has metastasised. So far, the politicians have been too terrified of an electoral backlash to make the cutbacks required to avert economic catastrophe. 'The news is so bad that scarcely anyone believes it,' says Ferguson. A more likely explanation is that politicians hope they can shove the nightmare on to the next generation of lawmakers.
Although interesting to speculate on the reasons why this potential crisis hasn't been addressed, the fact is that it exists independently of imperialism.
Colossus sells in the US under a less apocalyptic subtitle, The Cost of America's Empire, but both descriptions mask the fact that Ferguson has written a curiously bifurcated book.
That's not the case with Chalmers Johnson's The Sorrows of Empire: Militarism, secrecy, and the end of the republic, which is all of a piece: one frothing rant against America's 'permanent naval bases, military airfields, army garrisons, espionage listening posts, and strategic enclaves on every continent of the globe', which constitute 'a military juggernaut intent on world domination'.
Ferguson may think American imperialism has been undermined by clumsiness and inattention, but Johnson - an American expert on Japan - gives us an empire so far progressed that 'a revolution would be required' to block the Pentagon and the CIA's malevolent agenda. No doubt Johnson will appeal to some readers with his comparison of the US military to 'gangsters of the 1930s'. But surely many others will recoil from Johnson's more grotesque assertions, such as 'the murder of spouses' in the military as an example of the empire's 'values', and the preference of American troops to be stationed overseas, where 'the penalty for rape' is 'considerably less onerous' than back home.
Unlike the engaging Ferguson, whose arguments merit close consideration, Johnson seems destined to become a legionnaire in the empire of that other well-known documentarian, Michael Moore.
Colossus: The rise and fall of the American empire Niall Ferguson; Allen Lane; £20; MT price £17
The Sorrows of Empire: Militarism, secrecy, and the end of the republic; Chalmers Johnson; Verso £19.99; MT price £17.99. To order, visit www.mtmagazine.co.uk