California will NEVER leave the USA because it represents 55 ‘guaranteed’ Congressional seats for the Dems. Do you think that they will give that up?
Once they fully institute socialism, California will quickly go the way of Venezuela, and Cuba. No one within their borders should under any circumstances be allowed back into the US.
Actually if California votes to exit, it should be viewed as a state in rebellion. The military should move in, and the state of Jefferson created. The blue areas can go then go through reconstruction, where the Dems lose the right to vote for a period of time. The reconstruction shouldn't take very long, since all you'd have to do is clean up the voter registration rolls and conduct honest elections.