True but geographically and cultural, Oklahoma and Texas have been associated with the South. In reality, they are their own group but if you had to stick them in a cultural block, it would be the Southeastern United States before any other group.
There is just a lot in common between Texas and states like Tennessee and Alabama. Honestly, Ohio has started to share a lot in common with the South with the blue collar attitude. Michigan is a little more iffy.
Kind of a sad example, but I travel to Ohio a lot for work and I saw more Confederate flags driving through Ohio than I have seen in Tennessee (which is ironic since Grant and Sherman both came from Ohio).