Here is an interesting story depicting one scenario for the breakup of the US and an ensuing Civil War. It is followed by a series of letters from people giving their own take on how it might play out. Almost every one of them has Texas or California coming out on top. There are a few other contenders but none with the ultimate advantages that CA and TX have. I shuddered at the thought of my State coming under NY’s control.
http://www.quora.com/If-every-state-of-the-USA-declared-war-against-each-other-which-would-win