nascarnation is correct. There are simply too many people in every state dependent on a check from Uncle Sam. Suppose Texas says it is going to leave the union... in every state every city and small podunk town has HUD housing, food stamp and welfare recipients, farmers who get subsidies, old people on Social Security and Medicare, and on and on and on. Immediately, the Feds would cut off the funds - there would be riots, post offices shut down, old people without food and on and on. This is not the 1860s. People then could survive without Uncle Sam. For many people now, that is not possible. We are indeed slaves.
If Texas seceded the burden of no federal taxation would be an unbelievable wealth creator. Those actually needing help could get it directly from charities or churches.