To understand how much the Iraq war has changed the world, cast your mind back - not just one year to when the war started, but more than two years to when we first heard of the "axis of evil". Consider how far-fetched it seemed then that even a Republican-led America would actually start another war and that a Labour-led Britain would join in. Afghanistan was one thing. Many people rightly opposed that invasion, but saw that after grievous attacks on New York and Washington, the US could at least make a credible case for acting in self-defence against a specific threat. Iraq was quite different. Here, even if it had been true that Saddam Hussein possessed weapons of mass destruction, there was no suggestion that he intended imminently to use them. This was never a pre-emptive war, which implies an immediate threat of attack. Rather, it was a preventive war, designed to remove a potential threat and overthrow a regime thought inimical to American interests. True, preventive wars are nothing new: Britain launched one in the 18th century, called the War of the Spanish Succession. But most people outside the US believed such wars belonged to the distant past. The Iraq war was also (at least to some Americans) a crusade to light the fire of democracy in the Arab world. Crusades were something else that people hoped they had left behind.
To Europeans, this has been a deep shock. Before Iraq, the beginnings of what the American commentator and former State Department official Robert Kagan has called "a philosophical schism within the west" were already evident. Now, the two sides of the Atlantic are living, in Mr Kagan's words, on "separate strategic and ideological planets". A profound loathing of America has spread far beyond the sections of the left that have long denounced it as a capitalist behemoth. It has gripped Europe's business and professional elites who now believe that their continent must develop as an alternative power to the US (politically and economically, if not militarily) rather than as a partner. This schism will not easily be closed by the election of a Democratic president who will be a more consensual-minded hawk, rather than a dove. Despite its new friends in eastern Europe, the US, for the first time since the 1930s - when it deliberately chose isolation - stands alone. In Iraq, it forfeited the leadership of what used to be called "the free world".
Americans often accuse Europeans of being blind to new realities. But it is perhaps America that is behind the times in not understanding that its power has lost legitimacy. The existence of the Soviet Union made American power acceptable for several decades, not only in Europe, which faced what seemed real threats to its physical security, but also in much of Africa, Asia and the Middle East, where great-power rivalry allowed countries to play one off against the other, sometimes to considerable advantage. In the developing world, an accommodation with the US and US-led institutions such as the World Bank is now the only alternative to isolation and penury. But the US insistence, in the name of growth, liberalism and democracy, on deregulation, privatisation and openness to foreign trade and capital looks to many developing countries like a thin cover for the promotion of American commercial and financial interests.
Now Europeans also begin to smell a rat. The cold war allowed the US to dictate the terms of politics and trade across the democratic world. How convenient that it now identifies a new danger that requires it to exercise similar leadership. But even if they accept Islamic terrorism as a long-term threat, Europeans do not see how America can protect them from it in the same sense that it protected them from Soviet invasion. Americans frequently suggest that the real reason for French, German and Russian opposition to the war was that these countries had business links (usually clandestine) to Saddam, or plans to develop them. Europeans may suggest, with equal cynicism, that Saddam's overthrow opens new opportunities for US capital, many being exploited by contributors to the coffers of the Republican Party.
As Mr Kagan writes (in a new section of his influential book Paradise and Power, of which a revised edition is published by Atlantic on 20 March): "To the modern liberal mind, there is something inherently illegitimate about the idea of a single, dominant world power unconstrained except by its own sense of restraint." America might have got the benefit of the doubt, particularly if it had shown itself willing to stick with the United Nations, a body that became more, not less, important in the less stable world order after the end of the cold war. Instead, the invasion of Iraq confirmed everybody's worst fears: unshackled, the US seemed to behave like a classically aggressive imperialist power.
Even such an acute commentator as Mr Kagan in the end misses the point. "Not all hegemons are equally frightening," he writes. America, he argues, does not pose a threat to European security or independence. Europe's gripe is really that, "too weak to be a potential ally, too secure to be a potential victim", it has lost control over US policy and thus over world affairs. But many people do feel frightened, economically and culturally, by the American hegemon - and some, like Anatol Lieven, Mr Kagan's colleague at a Washington think-tank, fear that the US could yet take a more unpleasantly nationalistic turn. The US, by any standards, is economically and culturally aggressive; Iraq suggests to the world that, when thwarted, it will turn militarily aggressive, too. The belief that the US could be a benign power - the world's "last, best hope", as even many leftists once regarded it - has been destroyed by the Iraq war.