For the purposes of discussion, let us say that there would be a mechanism to permit a state to leave the union an be on their own. And let us assume that Texas would be that state.
What happens to the federal land and buildings and workers in Texas?
What happens to the share of the national debt that Texans owe?
What happens to Texans and Social Security and Medicare?
What happens to Texas and border issues - not just with Mexico but with the USA as well?
What happens to citizens of Texas who still want to be part of the USA?
What happens to citizens of the other 49 states who now want to move to Texas and their Social Security and Medicare and share of the debt?