I'm of the opinion that the US will almost certainly balkanize, and maybe it really wouldn't be the worst thing for pretty much everyone (the world included). There's something like 14 distinct regional subcultures in the US, last I heard, and I could easily imagine the US splitting up largely around regional boundaries. The biggest source of tension I foresee is figuring out water rights between regions. Maybe splitting up around major regional watersheds would be the best way to go.