Could it be as simple as a new US Government no longer recognizing USD as a currency, thus nullifying all debts? I doubt it, but something would have to give. Think about it, when you take out a loan, pretty sure the contract says it has to be paid in USD. If USD ceases to exist, couldn't the bank just seize your assets instead? I don't see any clear way that debt can be nullified for everyone even if the petro dollar ceases to exist.

Edit: NVM. I think I misunderstood your post

Could it be as simple as a new US Government no longer recognizing USD as a currency, thus nullifying all debts? I doubt it, but something would have to give. Think about it, when you take out a loan, pretty sure the contract says it has to be paid in USD. If USD ceases to exist, couldn't the bank just seize your assets instead? I don't see any clear way that debt can be nullified for everyone even if the petro dollar ceases to exist.