tsubaki
Player Valuation: £90m
Water supply and natural resources wouldn't be an issue for them, as they just import it. The US wouldn't switch off the taps on California - they'd just trade for it, like the USA has traded for oil with the middle east and so on.
Independence doesn't mean being like a video game and collecting resources to survive.
Again though, I couldn't actually logically argue for it myself, but my point is that it could become so emotionally tempting as a result of a lunatic Trump administration that a state like California would feel they had no other choice. It'd be like abolishing guns out of the blue - Texas and the likes would be clamouring for the same thing, and if it did go to referendum they'd be highly tempted to secede on that sole basis alone.
What would they trade, though? If you take away all the things that are only there because it is currently part of the US (and which would inevitably go back into the US if they split), you are left with agriculture (which is entirely dependent on water from the US) and solar power.
They could certainly make a go of it on that basis, but the state would look radically different from what the people advocating secession would want to see, and the control that the US would be able to bring about would make independence a bit of a joke; they could just turn the water off.
The difference between Texas and them is that Texas actually could stand by itself; it still has big energy reserves (a third of the US crude reserves, according to wiki), an independently viable agriculture sector, domestic manufacturing that would be difficult to move elsewhere in the US and which has global significance, and it isn't that dependent on the rest of the US.