GEORGE BUSH got in trouble recently for saying the tragedy of Iraq over the last year will come to be seen, in the long narrative of history, as a mere comma.

It sounded to his critics a little callous to dismiss the war as one of the commoner punctuation marks. Tens of thousands of casualties, the discrediting of a superpower’s foreign policy, the destabilisation of the world’s already most volatile region? You’d think that might at least merit an exclamation mark. But no. Just another dull comma, the notoriously overused dab of a penstroke separating much larger, substantive thoughts.

And yet commas, and their placement, as Lynne Truss has cleverly and lucratively demonstrated, can have large consequences. They can change the entire meaning of sentences. They can, on the one hand, represent no more than a boring, tiresome, repetitive pause in a long list. But in the right position, they can signal a critical dividing line, a caesura, as poets call it, a point of departure in a line of thought in an entirely new direction.

Which sort of comma will the Iraq war be? America’s critics and enemies hope, and some of its supporters fear, that the answer is obvious: Iraq represents a great dividing line in history’s multi-clause sentence — the end, or the beginning of the end, of the American century. The war itself, on this view, shows in unexpected clarity the limits of American power. At almost precisely the moment that the US seemed to bestride the world as no other colossus in history, it is felled, not by by a rival empire lobbing nuclear missiles but by a bunch of murderers armed with plastic explosives.

More than that, say the doubters, America’s famous “soft power” has been fatally undermined, victim of an ugly war, Guantanamo Bay and torture. At the same time, America’s costly detour in the Middle East has allowed new rivals to gain ground in the struggle for global hegemony. China and India, emerging powerhouses, are eating into global markets in goods and services, while the European Union, preaching love and peace, is winning the market in ideas.

As you might expect, I’m sceptical about the premature obituaries. That Iraq shows the limits to American power is surely true. But the only real surprise in this is that we should be surprised about it. Asymmetric warfare from Algeria to Northern Ireland has shown the limitations of large immobile militaries. With accelerating nuclear proliferation, those limits are only going to grow, as we have seen with North Korea. What will determine America’s ability to maintain its pre-eminence will be its flexibility and the willingness of its population to take on new burdens in the new warfare that confronts them.

Here, I suspect, the consequences of failure in Iraq are also overblown. The Vietnam War was a much larger calamity. By 1974 it had produced a precipitous decline in self-confidence and was tearing the country apart. But just six years later US voters elected Ronald Reagan, who placed American greatness and global pre-eminence at the heart of his presidency.

That America’s soft power has declined is probably true too. But I wonder if that is not mainly a consequence of the changed circumstances in which the US finds itself. Throughout its 220-year history, as the historian Robert Kagan points out in his brilliant new book, Dangerous Nation, America has been seen as a threat to global stability. But for most of that history, the US was just one of many powers. The angry backlash against it today is worse in large part because its dominance is greater than it has ever been. In a world in which America has no serious rivals, its revolutionary tendencies will inevitably be seen as more alarming than in one in which it has many competitors.

The real question about American power is whether the realities that underpin it are shifting. There, I’m afraid, the news for Americaphobes is grim. The US economy continues to grow at a pace that far outstrips its rivals in the industrialised world. Though China is growing at three times the pace of the US, America’s economy is so large — $12 trillion annually — that , even in the unlikely event that China will continue to grow at its current rate, it will take 30 to 40 years to catch up with America.

Despite the heated rhetoric, the US is not going bankrupt — its fiscal deficit is falling and its accumulated debt is easily manageable. Compared with most other advanced economies, its demographics look indecently healthy. This month the US population passed 300 million; it will be 400 million in less than 50 years, and still relatively youthful.

If you want to understand the real enduring strength of America as a nation, look at the Dow Jones industrial average. Not the record 12,000 level reached this month — that may last no longer than a day or a week. Look instead at the 30 companies that make up the Dow index. Only two of the original 30 companies in the index in 1930 — General Electric and General Motors — are still there today. Most of today’s Dow components — the Microsofts and Intels — weren’t even around 50 years ago.

If you look at the relevant stock market indices for Germany, France or even Britain, you will find them dominated by companies that have been around for generations. America by contrast, has mastered the art of creative destruction. This vast competitive openness, combined with entrepreneurial spirit, keeps the country constantly innovating and regenerating.

Long after Iraq has established itself as some kind of punctuation mark in American history, America’s genius for renewing itself will surely have the last word.

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