I FINISHED RICHARD MORGAN'S THIRTEEN, and it was quite good. Part of the backdrop for the story is a U.S. that has divided along the "Greater Canada" / "Jesusland" lines in that post-election cartoon. Morgan doesn't do much with that -- he's not an American, and he treats the flyover states as one big Mississippi, which would be irritating if it played more of a role in the story. Even Mississippi isn't really one big Mississippi in that fashion. One thing that he gets right, though, is that everybody's worse off from the change.
A post-secession America would be a better topic for a novelist with a lot of multi-culturalist chops like Tobias Buckell, somebody with enough understanding of America to pull it off in a way that Morgan was smart enough not to attempt.