Or Maine? Can a state pull a Crimea and vote to become an independent entity? I presume all federal aid and services would stop. But maybe Texas or Maine would be ok with that. What really prevents this from happening here?
States can’t unilaterally leave the country, but it looks like statehood is approved by Congress, so it seems likely that they can pass a destating measure.
Well, first Mexico would have to cross the border with a few thousand troops and some tanks, just to make sure the violence didn’t spill over into Mexico.
No.
In the early days of the United States, this was something of an open question, and there were a number of attempts at secession. But a definitive answer was handed down in the case of Grant vs. Lee in 1865.
Once again, people: the issue was settled once and for all by Grant v Lee, (1865).
No, they can’t. And they can’t be kicked out, either. The Constitution expressly forbids it.
Suppose Texas did vote overwhelmingly in a referendum to secede from the Union. Really meant it and willing to fight for their independence… Including guerrilla warfare.
Would the United States of today do a “Lincoln” and send its army in to forcibly occupy the State? Would every secessionist be considered a traitor and subject to the death penalty?
Would the USA likely be subject to international sanctions?
Yes, undoubtably. “Equal Protection” means that the US must defend every citizen, and I’m quite sure that no matter how many Texans voted for independence, several million would vote against it. The Amy would roll tanks, and every single one of the traitorous sons-of-bitches would be put up against the wall.
Doing a quick search for “Texas military base map”, it looks like the army’s already there…
Which would be a real savings on fuel! 
Of course countries can break apart without a war. Czechoslovakia did it, and Scotland which has been part of the UK for hundreds of years might do it. That doesn’t mean that a state can just hold a vote and declare independence.
Several states actually tried this in the 1860’s. You might want to learn about that incident and what the result was. I recommend a basic “History of the USA” book.
On the other hand there is the possibility of Texas dividing itself into multiple states:
Which would never fly because Congress would never approve it.
Although…if it was worked right, it could fly. Make Austin and surroundings a state, Dallas and Houston ditto, and the rest of the state can go hang. That gives us 3-1 blue v red, and the nutballs get even hinder-tit.
I like it!
Yes, but that was a case of “might makes right”.
Not sure if that would work that well today. The USA would be under tremendous international pressure to let self determination stand. And with our long history of favoring self determination we would not have a believable response.
Fine then. Let them leave. Once they pay for all Federal property within their borders, repatriate (with compensation) every US citizen who does not wish to go with them, and assume (and pay off immediately) their pro rata share of the National Debt. Seal the borders and shoot anybody who tries to cross into the US. Then drop a line to Mexico and tell them if they want it back, they are welcome to it. The US won’t lift a finger to stop them.
I’m not as stupid as I look, but thanks for the suggestion. Given that times are considerably different, given that the loss of tiny Maine, say, doesn’t present the U.S. with devastating economic upheaval, moral compunctions, or any of the main factors in “Grant v. Lee,” what actually would prevent that from happening?
The obvious fact that the US isn’t about to give up any of its states to another country. And no state, save maybe California (on its best day) could survive as an independent country. So why would we allow the formation of a new 4th world or worse hellhole on our border?
As has been said, precedent. No one will want to set a precedent that a state can leave the Union, since that could eventually result in complete fragmentation. Look what happened in the USSR and Yugoslavia. In the USSR, once the Baltics declared independence and proved it could be done, the rest of the country unraveled rapidly - including Ukraine and Byelorussia, which had largely been regarded as integral parts of Russia. If Maine is allowed to secede, then more vital states could be next.
Hah! So you admit that Putin has a point. Gotcha ya!
Yes, but only in the distant past – by the time the USSR dissolved, neither Ukraine (save Crimea) nor Byelorussia had been an integral part of Russia for over 70 years.