If US govt bond yields go up due to Congress choosing to default, you can bet the Vulture Capitalists will be buying as many/much of the defaulted paper as possible as fast as possible (particularly the short-term debt). Why? Because the US govt has (thus far, anyway) always paid its debts–and that won’t change with a delay in payments. The govt will add extra interest to their payment, when it is paid, because it is LATE payment. This has happened before and is no big deal.