Those places were largely from the Mexican cession. Said Hispanics left for Mexico after the Mexican-American War, and stayed there.
The New Mexican Spanish population (as in the hispanics who live in what is not new mexico) stayed there in OTL (i.e. before your POD). Do they leave after that? They're legally white, and I believe socially white as well.
The Hispanics aren't really an issue, so they're considered white if they look white.
No linguistic autonomy then? Weird given Deseret Utahans got autonomy (and Cajuns). Then again, the Deseretians were more...controversial to "Gentile" Americans given their distinctions were apparently racialized in ways (cause only non-whites do polygamy or whatnot, according to anti-polygamy groups).
The Mormons got autonomy because they were being a pain in the ass, while the Cajuns got theirs because it's part of the Federal plan to weaken the South. The setup of the UAFR has more to do with ensuring Federal supremacy than it does with a rational way of organizing societies.
Ahh. Looks like Im spoiled by the Soviets' border delimitations then D: