Deliberately defaulting on debts is probably the worst thing for a sovereign nation to do. The governments of other countries may still be do that risking higher interest rates as you mention. However, if the USG ever does that, there will be consequences far more dire than China or SSA or the Fed losing money.<p>And there are many reason for the low rate of interest, but historically, USG securities have been the safest investments, so you have a lot of dollars chasing them. So the USG can set the interest rate low and yet it will be bought up.