I don't believe you. Electric car charges don't use that much power, and they can be set to charge at night when the grid has a lot of slack.

IDK about replacing ALL regular cars, which isn't going to happen for decades, but just doubling them wouldn't cause the grid to collapse.

Teslas are about 0.25 kwh per mile. If you have a 20 mile commute, that is 5 kwh a day. Household kwh usage in California is already 6,000 per year.

The only stress on the grid comes from peak times, usually driven by air conditioning. Cars aren't charging at those times. They charge during the day when there is a solar power generation glut, or at night after demand falls off when people go to sleep.