A CDS can pay the difference if a government decides to pay a fraction of the full value. This has happened in other countries without total financial collapse

A CDS can pay the difference if a government decides to pay a fraction of the full value. This has happened in other countries without total financial collapse and could feasibly happen in the US if it has a president that actively wants to negotiate debt down. You could also purchase PUT options on a bond ETF like TLT where the counter-party will be the OCC, which will have little exposure to the turmoil in the bond market like a bank that would underwrite a CDS.