Heel n Toe,
Here are the 4 official regions (Census Bureau):
Notice the divisions as well.
Other agencies break up the U.S. land mass as necessary for their administration.
The Fish and Wildlife Service have there own map as you have shown. They put Hawaii with Idaho and California with neither.
While some consider Texas as part of the Southwest, that is certainly not universal. I don't think it is even the majority:
Southwestern United States - Wikipedia, the free encyclopedia
Heck, Kentucky and Tennessee were considered the west in the early 1800's and west of the Mississippi river was the frontier.....
Scott