There's more oil in other places then California so I doubt anyone would be interested.
There is plenty of water. You non coastal folk may have never experienced this thing called the ocean. Desalination is how many coastal countries get their water. That's some of that "science stuff" that they may not teach in the country's center states

As far as fruits and nuts, I think if it was cheaper to produce them somewhere else then they should. Farmers have unnaturally used up the ground water there given that it is 70 degrees and sunny year round allowing for continuous growing seasons.
I think many in California would love to not be apart of your KKK rallies and bigotry and if that means a separate country then so be it.