If the 20th century was the American century, it ended with the boldest of flourishes. In the final three months of the century, economic growth accelerated to an annual rate of more than 7%. Not only that but, thanks to a booming stock market, America's household wealth soared by dollars 3 trillion (pounds 1.8 trillion). To put that in perspective, the booming US housing market of the 1970s produced a wealth gain - in today's prices - of dollars 2 trillion for the entire decade.
In February, America notched up her longest ever economic expansion, beating the run of 1961-69. As a wealth-generating, job-creating machine, the US economy is unrivalled. With this growing economic power has come the near hegemony of the American model.
America in the 1980s, with her public finances in a mess, her productivity growth chronically low, was nobody's role model. Then, people spoke of the intellectual and practical superiority of Germany's Rhineland model, or the Japanese approach.
Today nobody does.
With its budget surpluses stretching into the indefinite future, and with an economy that has adapted effortlessly to the productivity-enhancing effects of new technology, America sets the standard. Who is the world's most respected central banker? In the old days you would look to Frankfurt and the Bundesbank. Now it is Washington and Alan Greenspan.
Nothing lasts forever, though. And we have seen some of the first intimations of mortality for America. The 35% fall in the Nasdaq index of mainly high-technology stocks in the four weeks from March 10 represented at least a mini crash. America's long bull market has had its wobbles before, but this one produced soul-searching about where the economy is heading.
Two questions dominate the discussion. The first is whether America can come down from that 7% growth rate and achieve a soft landing. The second is whether the rest of the world will be content to finance a current account deficit of dollars 400 billion a year and rising.
On the first, even his supporters are questioning whether Greenspan's apparently sure touch has deserted him. As for the second, economists increasingly worry about the sustainability of a foreign imbalance of this scale. According to John Makin of the American Enterprise Institute: 'The dangerous underpinnings in financial markets of the 5%-plus growth rates of the US economy constitute a familiar story replete with potential problems ... The Federal Reserve's excruciatingly slow 'no surprises' approach to raising interest rates is beginning to look like a policy mistake that will see US demand growth continue to outstrip the willingness of the rest of the world to lend the United States dollars 1.3 billion a day at current interest rates and exchange rates.'
We know how America's economy got to where it is. With the rest of the world apparently condemned to slow growth, the US could not only safely grow fast - without triggering higher inflation - but it was beneficial as 'consumer of last resort' that it did so. Meanwhile, booming job growth and a rising stock market created something like a perpetual motion machine, in which wealth creation fed back into stronger economic growth, in turn creating more wealth.
We also know, however, how America will come off its pedestal. At some stage, international capital will seek other homes, whether it be because Wall Street is perceived to be too risky or because there are more favourable investment opportunities elsewhere. As Gerard Lyons of Standard Chartered puts it: 'At first US stocks will fall. This will lead to volatility, as many investors will buy equities on weakness. As it becomes clear that the Fed will not cut rates but will keep raising them, the equity markets will become more volatile and trend lower. Soon it will be the dollar that suffers, followed by US bonds. The US faces a triple whammy of weaker stocks, weaker dollar and weaker bonds.'
A financial market correction of this kind may be no bad thing. Makin warns, however, that bringing the US economy down to earth could involve a bumpy landing. He sees the risk of falling output and rising inflation - in other words, stagflation.
Were this to happen, there would no doubt be a large element of schadenfreude elsewhere in the world. On a trip to Tokyo I was discussing the problems of the Japanese economy with a businessman. 'Just wait until America crashes,' he said. Europe has also got fed up with being lectured about the superiority of the American way.
I hope the US economy can avoid a hard landing, for not only America would suffer. There have been false dusks for America before, and this may be another, although the risks have increased. But what I hope even more than that is that, in the event of a hard landing, we do not throw the baby out with the bathwater. The American model of a dynamic, innovative, enterprise economy is better than anything else available. Far from deciding it is past its best, we all have a lot still to learn from it.
Visit David Smith's web site: www.economicsUK.com.