There is no codified legal process for a US state to leave the Union, and the only previous attempt caused a civil war
A member of the EU has both an implicit right to withdraw from the treaties (deriving from international customary law around treaties) and an explicit legal path to follow. A process which they control in their entirety (as in they can't be forced to stay longer than they wish by the other countries and can't be forced to leave earlier than the prescribed deadline)
EU treaties explicitly say that a member can leave them (in particular article 50 of the Treaty of the EU).
In general a country can't get out of an international treaty unless the treaty itself has provisions for it. Of course the only way to enforce an international treaty, if threats or sanctions are not enough, is war.
Every free trade agreement is a political endeavour. The entire concept of free trade is in part where the term "liberal" originates from (not that the term should be considered a guide to current policies of parties with that title, lots has changed since it was Liberals vs Whigs).
Indeed it is not a country. But democratic process is a very wrong word here, even with the adjective "representative". The EU process for updating its own rules is a bureaucracy directed by prime ministers, and those influenced/controlled by powerful groups. E.g. Scholz and Macron pushing for federalization and weakening the power of states - this is great for EU apparatus and those wanting to make it stronger, but state citizens do not want this.
I wouldn't connect those concepts at all. Democratic process is expected in a state that proclaims to be a democracy. Not in a trade agreement of multiple states. Also, EU is not just a trade agreement.
Really? You mean that there is something in the US Constitution that explicitly allows a state to secede?
"In the public debate over the Nullification Crisis the separate issue of secession was also discussed. James Madison, often referred to as "The Father of the Constitution", strongly opposed the argument that secession was permitted by the Constitution.[29] In a March 15, 1833, letter to Daniel Webster (congratulating him on a speech opposing nullification), Madison discussed "revolution" versus "secession":
I return my thanks for the copy of your late very powerful Speech in the Senate of the United S. It crushes "nullification" and must hasten the abandonment of "Secession". But this dodges the blow by confounding the claim to secede at will, with the right of seceding from intolerable oppression. The former answers itself, being a violation, without cause, of a faith solemnly pledged. The latter is another name only for revolution, about which there is no theoretic controversy."
If things went so far that the secession is desired it is already a civil war, and constitution of 'some people out there over the creek' doesn't matter.
The 26 cantons are mentioned in the Swiss constitution by name. If one wants to leave, the constitution would have to be changed. So a canton can only leave, if a majority of the whole people as well as the cantons voted in favour.
There is no codified legal process for a US state to leave the Union, and the only previous attempt caused a civil war
A member of the EU has both an implicit right to withdraw from the treaties (deriving from international customary law around treaties) and an explicit legal path to follow. A process which they control in their entirety (as in they can't be forced to stay longer than they wish by the other countries and can't be forced to leave earlier than the prescribed deadline)