In addition to the FDIC backstop mentioned by some of the other responding comments, there's also another significant factor here which is that the U.S. banking

In addition to the FDIC backstop mentioned by some of the other responding comments, there's also another significant factor here which is that the U.S. banking system is ultimately backed by the strength of the U.S. military. I think this serves as something like an inductive base case that is more important than it might seem at first glance.