We've had an active separatist movement in Canada for years now. By Supreme Court decree, if they ever get a "substantial majority" of support for separation, then the federal government must "negotiate" a separation settlement.
Basically, this means that if the separatists ever win a referendum (and they've come close), they'll argue with the feds over specifics for a while and probably give up. Because that's the Canadian way when it comes to constitutional issues regarding federal/provincial powers: we argue about it for a while, then we decide it's too much of a pain in the ass to figure out.
But seriously, Texas? I can see the appeal of that proposal that occasionally goes around to form a country out of British Columbia, Washington State, and Oregon, but that's the Pacific Northwest and Texas is, well, Texas.