Oh yes, they are down in the dumps all right with 9% unemployment and a budget deficit which is 10% of their GDP. They have to do something very drastic and do it soon if they are to come out of this mess anytime soon. However, it will be tad premature to write them off yet. The internal conflicts of the US will bring it down. Their Military Industrial complex, the Corporate manipulation of the American democracy will bring it down, not Iraq or Afghanistan. The American Laissez-faire will bring it down. Remember Ayn Rand? Totally rampant and unregulated capitalism will bring down the USA. But not in our life time, I think.
The only thing that saves US at the moment is that the US$ dollar is the reserve currency. the brics have already along with many other countries have suggested that this should be changed. Its only a matter of time and in my opinion this will happen within 5 to 10 years. Simple mate you cant live beyond your means.