Here is a map of the North American Tribunals in our saga set in modern times. Blue lines are tribunal boundaries, green lines are Ley lines.
Why is Texas its own Tribunal? Why, because Texas!
This would make a funny meme on the ars magica sub reddit.
They seceded from the Mexican Tribunal, of course:)
Actually no, but maybe I'll retcon that into saga history.
The fact that I myself am a native born Texan probably doesn't have anything to do with it...
While not native born (I transplanted from Louisiana when I retired), many members of my family are native born. From personal experience I will say that you being a native born Texan most assuredly has nothing to do with it...