By the 1800s, Texas was an independent nation. I'm from Texas. My character is a cowboy. Can The Republic of Texas be a thing? Please? Pretty please? It would really, really make my day, and would be era appropriate.
In the actual history, Texas was originally part of France, then sold to Spain, then when Mexico rebelled and gained their independence from Spain, it was part of Mexico. Then Texas, which was mostly American colonists at this point, rose against Mexico and won the war, claiming their independence, then about ten years later agreed to join the United States, mostly because the US and Mexico were getting ready for war, and Texas didn't like being in the middle of it.