It would be Biden’s default
There will be no reason for the US to default on its debt. The US has more than enough money, coming in to pay interest, debt that it is due, Social Security, Medicare, and Medicaid, and more. The Constitution requires that Biden pay the US debt. If Biden decides not to pay US debt and there’s a default, it is all on him.
https://twitter.com/moxlosllc/status/1649038920447848448?s=46&t=Y4fVsDnz2q8uZ3VNKeco4A