Normal democratic norms allow the majority to overrule the minority. But the minority has a check and balance in Senate malapportionment.
But perhaps this can be solved by comprehensive self-determination. If the People are set to acknowledge the right of States to secede from the Union, perhaps counties should be allowed to secede from States? Before California Secession becomes a serious issue, shouldn’t each county hold a referendum on whether or not it wants to remain a member county of the State of California?