Consider also Amex Premium Car Rental Protection
This is a special Amex program that you have to register for and be linked to your Amex card, I think possible for any Amex card.
If you use the registered Amex card for a rental - Amex charges you $18 for Entire rental period (for CA, maybe $20-25 other states).
You get super primary coverage for rental car upto $100k + medical, property etc.
I once did a small dent in a rental car and Amex took care of it like I was a VIP customer.
I discovered it when I was searching for coverage for SUV rental in Costa Rica. Most CDW programs of CCs say for SUV "only on paved roads" and in Costa Roca most roads are not paved.
More details... you need to review the official program description.