The United States has to be a hated regime. It can do something like keep and expand slavery (or even re-legalize slavery in the North), fall to a brutal military regime, explicitly refuse to integrate. In a nutshell, it has to be racist, theocratic, or under some horrible right wing dictatorship, but you can play your cards as long as you don't make the U.S. communist. Any POD allowed.
No OTL comments(this U.S. is almost universally hated in TTL)