I occurs to me that I don't really think of Texas as being in a region at all. I just think of it as Texas- big enough to be it's own region, really. (Also, west Texas is southwestern, and eastern Texas southern, because the two areas are so geographically different.)

And you're right- I wouldn't blink at Cleveland being mid-west, but I don't put Ohio there. (I'd swear there was some separate grouping we did in school of 4 or 5 states that were basically all drained swampland- I thought Ohio fit into those, but can't for the life of me think what that was called now.)