No North American nation claims allegiance with Republic of Texas. Oklahoma is considered a protectorate state, which indicates that Texas takes anything it needs from within Oklahoman borders. The Texas Rangers provide protection whenever they feel that another nation is seriously infringing on their state's "turf." Most North American nations treat Texas like nitroglycerine: with great caution, lest it explode violently.
Texas, for its part, has little good to say about anyone. Texans currently reserve their greatest animosity for French Louisiana, particularly the air wing of the French Foreign Legion that recently arrived from the Spanish Civil War front and now patrols the Texas border. Next in line is the Confederation of Dixie, if only because of England's meddling in North American affairs by assisting that nation. Texas reviles Dixie even more than it does Free Colorado , the base of a recent heavy pirate raid that smashed the city of Amarillo.
The nation of Arixo has no trouble with the Republic of Texas at the moment, though the government is aware that Texas is casting an eye toward Arixo's mineral-rich lands. Texas has considered Mexico beneath contempt ever since the Second Battle of the Alamo; they don't think much more of the People's Collective, even though the Dusters recently put up a good show against Texas Rangers who strayed into Kansas Territory.
Of the rest, no one seems willing to align itself with the generally hostile Texans, though mutual enemies may make necessary allies. Internal political pressure in Hollywood (largely applied by Howard Hughes, who was born in Texas) might aid an alliance with Texas, and the I.S.A. might welcome aid against the People's Collective, but these alignments remain speculation in political circles. What actually happens remains to be seen; many fear, however, that given Texas recent drought, they may once again start annexing neighboring states to claim agricultural resources.
The President of the Republic of Texas, Austin Crockett, is the front man for the oil barons who rule the nation. The most powerful of these barons is Jackson Coe, a bellicose, gruff man who has used a large percentage of his wealth to finance the Texas Rangers and provide security within the Republic's borders. Crockett is a powerful and charismatic public speaker, popular among the Texans, but widely lampooned in the Empire State and Louisiana (which has, of course, caused no small amount of hostility between Crockett and the leaders of those nations).