Secession is one option, I suppose. Another is “federalism,” and, unlike secession, it has the distinct advantage of being how the country was supposed to work in the first place.
Because they understood how intellectually, politically, and economically diverse the colonies were, the founders invested relatively little power in the federal government. Indeed, they ensured by law that it could only do a few enumerated things, and they left the rest to the states. Mostly, this was a good idea then, and it is a good idea now, especially given how divided the country is. (The glaring exception, of course, is Civil Rights, which must, must, must be a federal concern.) If Californians so wished, they could use their influence in Congress and elsewhere to limit the reach of Washington D.C., and thus of the world’s Donald Trumps. Why don’t they?
The answer, I think, is that the temptation to control is stronger than the fear of losing concentrated power.