Such a deal is basically not possible. See the Argentina "pari passu" fiasco. Because US T-bills are everywhere. They are, to use a Claude-ism, load bearing for the world economy.

There is no "adults outside the room" who can intervene to fix the situation. Either Americans sort things out among themselves, or they will end up with the traditional Latin American solution to a debt crisis: hyperinflation. Which some of the right have been salivating about ever since FDR.