The debt ceiling has been a fair cause for concern in the American houses of parliament, and as usual, the republicans have found what was once neutral ground (the debt ceiling) to be their "give". It should be noted, that even that was hard won.
The entire American economy is based on a system of debt, and postponing payments of this debt. China is in no position to reposes the US, and simply by the mass of the American GDP, will always have an A+ (or greater) credit rating. The states, on the other hand, may still faulter, even as spending is cut and taxes raised. Additional taxes levied by the federal gov't on the top 1% of earners, might fuel a fund to give grants to bankrupt states.