Ironically, playing around with default actually makes treasuries more attractive

[Recursion]

The markets that are about to get pounded are securities and high-yield bonds. People have been running to treasuries so fast that the yield on some is actually negative at this point (people are paying the Treasury to hold their money for them).

This seems counterintuitive because it's the treasuries rather than the high-yields or stocks that are in direct danger of default, but that's the funny thing about economies: everything is connected. If we were talking about an Argentina-style default things would be different, but we're just talking about delaying some interest payments for a while. The main result of that is that interest rates will shoot up, which will hurt everybody with a long position on high yield bonds, and suck enough liquidity out of the still-dazed commercial paper market that most securities will take a big hit.

So, in another chapter of this hilarious fiasco, the result of a default on treasuries may well be an unprecedentedly large movement towards treasuries by investors.