On the large earth maps (including double, quad and mirror earth): Southwest-Gulf Coast (in the US)
And, more obvious: Rocky Mountains-Gulf Coast!

this is really more of a POV connection..
I always viewed it as not belonging purely due to the difficulty of sending troops through the oklahoma strip *-whatever it's called-* without also owning Texas

although logically, it's not much different then Tennessee - western great lakes.. which also feels really weird to me each time I see it as an option..