If the United States stops paying its bills, who can sue?
Potentially, at least, it's a staggering answer: In all, the U.S. government cuts about 100 million checks a month, including to Medicare and Social Security recipients, bondholders, and government contractors.
OK, let's assume all the various groups could get past that whole "sovereign immunity" thing...
Couldn't you just see some sheriff's deputy padlocking the doors to the US Congress? If the government was smart, they could sell tickets to that event and retire a substantial portion of the national debt.