@Oryxslayer maybe you can help with this but here’s my idea:
Eastern: lot of Cajuns and Anglos along the Gulf coast as well as urban areas. Most liberal part.
Hill country: Rural. Anglo-Hispanic settlers throughout. Kinda Conservative(except for Austin)
Southern: Mostly hispanics. Not a whole lotta immigration but there is some. Swing region.
Trans-Pecos: Similar, although El Paso and Albuquerque are pretty liberal.
Territories: Sparse, almost entirely hispanic, and conservative.
I like it. Also remember if it is a brazi analogy, then there will be left leaning slums. Also, would Austin even be a thing? This Texas I thought got free in the late 19th/early 20th in something similar but much more chaotic then the Mexican civil war.