The downgrading of America is a humiliation for a nation constantly fretting about its potential decline. It reinforces a very common belief here, that the squabbling politicians in Washington are to blame for many of the country's ills.

It was indeed a major theme of candidate Obama that "business as usual" couldn't continue and, by an effort of will, America had to come together.

The decision by Standard & Poor's to push America into the second division, when it comes to trustworthiness about paying its bills, puts the USA below the UK, Germany, France, Singapore, Finland and 14 other countries.

The reason it gives is what all America has been saying: Washington doesn't work. The S&P report says: "The political brinkmanship of recent months highlights what we see as America's governance and policymaking becoming less stable, less effective, and less predictable than what we previously believed."

A clumsy sentence, yet it encapsulates the frustration of many Americans. They don't think too much of the plan they did eventually come up with at the last minute.

"Our opinion is that elected officials remain wary of tackling the structural issues required to effectively address the rising US public debt burden in a manner consistent with a 'AAA' rating and with 'AAA' rated".

They warn America's debt will continue to balloon and they have little hope of the politicians fixing it.

They say they think dealing with the debt remains a "contentious and fitful process". They say no-one is serious about dealing with the programmes that eat up money, like Medicare, health care for the elderly.

They single out Republicans for ruling out tax rises. "It appears that for now, new revenues have dropped down on the menu of policy options... Compared with previous projections, our revised base case scenario now assumes that the 2001 and 2003 tax cuts, due to expire by the end of 2012, remain in place. We have changed our assumption on this because the majority of Republicans in Congress continue to resist any measure that would raise revenues."

My colleague Robert Peston has an excellent blog on the economics of this, but what about the politics?

President Obama will doubtless use the occasion to scold Congress again and urge politicians to come together not as Republicans or Democrats but as Americans. Some may be chastened enough to do that for a while.

But is fair to put all the burden on the legislators, as though failure to agree a consensus is a moral lapse? The president is fond of saying that Americans vote for divided government not dysfunctional government.

Yet the system, a much-loved relic of a different age, constructed for reasons little to do with the 21st Century, is almost designed to bring about dysfunctional government. The combination of a strict separation of legislature and executive, plus two-yearly congressional elections, all but encourages having different parties in control of different bits of government.

Americans are likely to bemoan the failure of politicians to bridge an apparently unbridgeable gap between two different world views. They may put their faith in Washington politicians, in an outburst of patriotism and goodwill, stumbling on a synthesis that suits all sides. But I wonder whether any of them will muse that the system itself may not be fit for purpose.