The Constitution of 1789 created a new national government ratified by a popular vote. Though the vote was organized by each state, ratification depended on the popular vote of each state not the individual approval of the state governments. The state governments assented to be bound by approval of 2/3 of the states' popular votes. This created the odd situation of each inhabitant being a citizen both of the state and of the nation, or dual sovereignty. This is something most foreigners simply give you a deer in the headlights look about if you try to explain it to them.
It would seem to me that any secession would need to be run in reverse, with a petition to amend the Constitution to allow that state to leave pending approval of 2/3 of the each states' population in a referendum.
“a citizen both of the state and of the nation, or dual sovereignty.”
US citizens are sovereign to the United States republic only. They may be residents anywhere in the US, and not necessarily in any State.
One could live in WA D.C. or a territory or an overseas military base and have an unconditional sovereign citizenship.
I was born in the territory of AK and had to do nothing to be a full citizen.