The USSR was composed of distict populations with different languages and cultures. Many of the republics had been independent countries- Baltic states, Armenia, Ukraine at various times in the past. CA is diverse, but not to the extent if the USSR.
I don’t think CA could defend itself.
Although a minority there are a considerable number of regular Americans that inhabit the north, the valley and most inland areas. These people would side with the US, just as WVA sided with the union.
Then, the US fleet in SD would control all commerce entering CA ports from the Pacific easily blocking any aid and from the Chicoms.
The metrosexuals from SF and LA are not Johnny Rebs.
The South is as different from the North east as Ukraine was different from Russia.
How does a country like Portugal defend itself with a per capita income about half of CA? CA would be first world country if independent.
There won’t be a war because bellicose idiots like are the minority.