There are Mexicans. The phrase Latino is there for your convenience.
Latin America comprises Mexico and points south. Both Mexicans and Brazilians, and Argentinians, and Peruvians speak Spanish....or Portugese (before the haters step in). You don't want to call a Brazilian a Mexican. Just like YOU as an American wouldn't want to be called a Canadian because you're from North America.
Given that you're specifically from Texas...you probably wouldn't even appreciate being called a Californian. Or a Yankee.
Get it?