All those sayings like you can't squeeze blood out of a turnip don't apply here. This commonly held sentiment is actually a gross misunderstanding of macro econ and the Current Account (balance of trade).
During the days of Adam Smith's Wealth of Nations we finally realized wealth is in the production and services a nation has to offer. Fiat and debt are backed by that alone and not by some nominal face value or military might. America is the most productive country in both total output and per capita.
We've actually been been begging China to dump there treasury holdings of US debt. The result would be massive export increases at home, more jobs than we would want, huge inflationary pressure at home, sharp increases in interest rates, large wage increases, a weakening of the dollar on the exchange, and a lowering of the national debt increase (in a vacuum not counting on congress changing in response).
The bottom line is yes America can pay the national debt that any nation holds over us. There is absolutely no need or even a plausible reason to war over national debt. The exporting nation simply needs to spend the money on US goods and services as the international monetary exchange system is set up to do.
