The government doesn't need collateral, they use yours.

Seriously, government debt is backed by the fact that the government has the legal right and the practical ability to confiscate as much of its population's wealth as it feels like. I don't like US government debt at all, but it's nowhere near the point at which the don't have the ability to pay it back.

Are you sure? He government can try to tax everything and use my PlayStation and house in Ohio to settle a debt to a Chinese citizen, but if it ends up destroying the US economy, there won't be any new wealth creation to tax, and that is where most government revenue comes from.

It is far more likely that US government will do what it and every other government always has done: either inflate the currency or default or declare war or some mixture thereof.

If the Feds start confiscating Ohioan playstations to payback chinese citizens, how long would it be until the states themselves revoke thair consent to be governed by the Feds? (See American Revolution, Articles of Confederation, and Confederate States of America),