Many countries around the world are the size of US States. The UK and Germany are only twice the size of California, for example.

The problem in the US isn't that we can't do things, it's that nobody can agree on what to do. And to solve that problem, let states do their own thing as much as we can, and it'll become obvious where the good systems are.

Or in other words, an argument needs to be made why the EU "works" with individual "states" doing their own thing, but the US cannot "work" unless it's considered as one large country.