The US is a truly gargantuan country; large states like Texas are already richer, bigger, and more populous than many or most independent countries. In fact Texas once was an independent country.
Texas existed as a self-proclaimed sovereign nation for the better part of a decade.
It began with the Texas Revolution and independence from Mexico. (Remember the Alamo!)
Texas immediately wanted to be annexed by the U.S., but the U.S. was reluctant about a potential war with Mexico. (Which when Texas was finally annexed, is exactly what happened.)
