Where would you even go if the US defaulted? It's such an armageddon level event that I don't know how you even begin to hedge it.
Longer-dated Treasuries. This is a technical default, and when threatened in the past, other Treasuries rally. The problem is if someone needs liquidity in an affected issue, or if this prompts a general risk-off mentality which then leads to rising capital costs across the private sector.