I've read so little so my input is questionable at best, however if I was to start a takeover like some of these folks are pontificating I'd start in Texas too.
Why start in Indiana and Ohio, sure they'd be easy pickings, over in a week, but why warn all they other, more heavily populated and armed areas that I'm on my way?
I'd have twice the casualties and the longer it dragged on the less support (if I had any to start) I'd have from other government agencies and the populous.
This would not be the type of land warfare where you start at one end and head to the other but a protracted gorilla war in which really no one wins. Then it's up to the Press and how much guts they have, will they show the cops/army rooting out pockets of resistance as brutality of the armed forces on the citizens or how the rebel citizens keep resisting "popular mandates" and should be eradicated?
Buy if you knock off the big one off to start, the others will fall in line a lot quicker or face the same fate.