They were Texicans if they were in Texas. At least my ancestors considered themselves not Mexican, not American, but Texican. Wasn't it Davy Crockett who basically told America to go to hell, because he was going to Texas? As for Catholicism, others may know history better than I do, but one of the hallmarks of the Mexican government (after independence from Spain) was to stymie Catholicism.
Oy. Not what I wanted to do, but...so be it.
You know what your ancestors thought? Amazing. I have family members who died in the Mexican War, men from North Carolina, Tennessee, and...Texas.
I think I know how they thought. Remarkably, many of them left letters, bibles, etc. One of the guys that died left letters to home. Mostly he just talked about how he wanted to get it all over with. Guess it did. For him, at least. The others talked about "fighting the oppressors". Since these were men who were about 2 generations away from the Revolution, I can only think that they regarded the Spaniard hierarchy as the sort of feudal hegemonists that the English Kings and Nobles were.
Which, of course, is correct.
As far as the Spaniard land grantees still in "Tejas", or rather Coahuila y Tejas, I have only opinions. I have found that some fought with the Anglos. Not surprising; every war has fuzzy lines of loyalty, some crossover. Santa Anna made few friends, as he was clearly looking to be a king. But in large, I don't see any mass opposition to him or the new "Mexican" government of 1821 among the descendants of the land grantees. Why should they? Bad as Santa Anna's government might be, he wasn't about to confiscate their dirt.
They could not make the same conclusion about the Americans. So I doubt that they were all just one little gang of go-getters, ready to start their own little planet.
I did a bit of research on the grantees a few years ago. The records kept by the Spaniard Crown, and their appointees in Nueva Espana, were quite thorough. What was remarkable was how few they were in the area west of the Bexar, and how large the grants. Ranchos of 48,000 acres were quite common.
It must have been a tough life: really on their own.
But then....the Anglos came. And the grantees became rather a small proportion of the population in a short time.
And that's what really happened. The few who went along with the Americans? They were a few. The rest...stayed loyal to who you'd expect. In 1846, it got worse, and in 1848, went downright bad.
As for Catholicism and Mexico....yup, they've gone up and down. But are you seriously trying to say that somehow, Spaniard Catholics were politically similar to American Protestants, because Mexico after the 1821 Revolution blamed the Catholic church for the previous 300 years of oppression?