I’m not so sure on that.
As pointed out in one of the other threads the 10th Amendment says “powers not delegated to the United States by the Constitution, nor prohibited by it to the States, are reserved to the States respectively, or to the people.”
The Constitution makes no mention of secession therefor it’s a power reserved to the State. Far as I am concerned Constitutionally States can and may secede if The People of that State vote to do so, probably through the State’s Constitutional process.
That doesn’t mean though that the USA has to just let them...we know how that worked out last time.
Also the world opinion would matter if a state chose to secede. How can we tell Russia to let Georgia secede, but not one of our states who voted freely to leave the union they joined?
I’m not advocating it, but just saying it would make most of our foreign policy that much more difficult if we are fighting to keep our states as part of the union and fighting for other countries to allow states to leave their union.