Virginia seceded, and the area of West Virginia did not. Instant new state.
Yes, this would be appropriate for California. Let the large cities and illegals demand secession (you can bet a lot of illegal La Raza will vote for secession). Create East California out of the area not seceding, and then go in, occupy, and name the remaining West California.
Nobody is going to “go in and occupy” CA if it secedes. Nobody wants a war. Nobody cares.