Sean O'Grady: The stamina may not be there to sustain this recovery

Oddly enough, it might be best to think about the US economy as a sort of tandem bicycle. In normal times, it has two riders pedalling it along the road to economic growth – the private and public sectors. Needless to say, the private sector has been flagging and the authorities have had to take up the pace, energetically: a multi-trillion dollar banking bailout; a $787bn special fiscal boost, contributing to a total budget deficit of $1.5trillion; the "cash for clunkers" scheme; tax credits for first-time home buyers and the Fed's near-zero interest rates and quantitative easing – injecting money directly into the economy.

Now it would have been a bit of a shock if the American economy had not shown some response to the vast sums lobbed at it. Indeed, much earlier on in this recession president George Bush's programme of emergency tax cuts yielded a similar boost. The problem, of course, is that that boost did not last, and neither can this one. The authorities don't have the stamina (the money, that is).

The collapse of the dollar – a disaster as far as the greenback's status as a reserve currency is concerned – is, if anything, a blessing for Americans, if it means that their vast trade deficit with China – the root of much economic evil in the world – is at last brought under control. America's bubble was built on huge funds borrowed from China by the private sector. Now America's recovery is being built on similarly extreme borrowing by the public sector. The grotesque imbalances remain.

All this borrowing may have got the tandem moving forwards again, but it still feels wobbly.