Yep. The central valley is hard to determine which way it would go. The large rancheros that have existed before Kalifornia are still very much Mexican at heart. But many of the farmers are Jeffersonians.
So, i really don't know which way they would go.
However, there will be the state of Mormon. Because they will defend it, and no one will want to dispute them for the area. (you'all can have it)
This is kinda interesting addition to that thought from history.
Looks almost like New North Mexico.
The Mormons can fight Mexico for territory, they've got history with being brutal.