No, and I honestly don't get why people argue this. Did texas have the right to join the US peacefully, without the rest of the country's approval? no, so why should it be allowed to leave without the rest of the country's approval? That being said, all that would be required for us to leave would be an act of congress + presidential approval, same as the annexation act, no constitutional amendment necessary. It would take some huge concessions, like taking a fat chunk of the national debt with it, some LBJ-esque backroom dealing texas politicians, and a well funded PR campaign, but given it's heavily in the democratic party's best interests I dont think it's beyond the realm of possibility.
if you think there's a lot of support for texas independence now, watch what'll happen if they try to restrict gun rights. that there'd be whatcha call a "line in the sand" issue
ETA: i really only answered this with regards to texas, but since it was the only state with an existing government before it joined, and other states never had the right to vote to join or not, i guess the question at least merits the argument that they should. It should at least require state and federal amendment though IMO, only a simple majority would severely weaken the country, as every state that disagreed would leave, thinking they would be better off, and almost always being wrong about it.
This post was edited on 12/13 at 12:22 am