Justinian
The consitution charges the Congress to uphold the full faith and credit of the USA. So we can't constitutionally default
We can amend the constitution...but I doubt it would pass.
In 1906 the Springfield Armory adopted a .30-06 rifle that used a Mauser bolt assembly and paid royalties to Mauser. When we went to war against Germany the royalty payments were due on every rifle made to fight the Kaiser--they were paid--into a trust fund; Mauser got the money after the war.
In 1941 all royalties to Axis countries were ordered put under US govt trusteeship...W Bush's granddad got busted for acting as a shadow trustee for Axis corps...they wanted Bush to manage the accounts becuase as a shareholder he'd try to make more $$$ whereas FDR's lawyer naturally didn't give a damn about earning $$$ for German firms.
The other trick I've mentioned, have 50 states secede from the USA, keeping DC and Indian reserverations and Puerto Rico and Guam as the United States...which would keep $16 trillion in debts...and the other 50 states would form their own debt-free country. XD