If the USA had to change from federal to Unitary or Confederate, which one?

[angus]

confederacy* (I/O)

*local option regarding local tax and zoning laws, but with open borders and a common currency.  Something like the Rheinbund, but without aristocracy, kings, dukes, or Napoleon.  That confederation was above all a military alliance, which I think is the important part:  common defense.  Let each decide how good its schools and hospitals ought to be, but there should be free trade among them and a common army and navy for the protection of all.  Also, there should be something in the original contract about not allowing extermination of all aliens, as in the current episode of Supergirl, and in the current presidential administration of the United States.