Heck, if Texas wanted to secede, they'd have to do so out of force. America's got a funny way of creating laws which couldn't possibly benefit society.
Why fight? Not like they can't just circle the place with fence and lock everyone inside, shoot any incoming air traffic down. I think it isn't exactly the greatest idea to be isolated nation inside unfriendly one...
It's exactly like that, actually... Texas has major ports, rail and roadway hubs, and a very large stretch of border - including some with Mexico. Even if they could, cutting off trade through, or with, Texas would be a very damaging thing for the US to do to themselves.