The supply amperage has no bearing on the type of socket, most but not all in France are now the same blue '16A' style as we have here in the UK. That being said I always carry a Shuko type plug (
https://cpc.farnell.com/c/plugs/schuko-plugs) with a short length of flex and a '16A' style socket on the other end just in case. Many campsites will be able to lend you a suitable adaptor should you need it.
As for polarity reversals I don't worry too much about it as I always rely on un-pluging any appliance to be sure both connections are disconnected. All other items in my camper are double insulated.
I would assume that a California is designed to accept either polarity without problems as it is produced in a country where such occurrences are common.
If it worries you, carry a socket test plug (
https://www.toolstation.com/socket-tester/p82826) or similar and make up a very short lead extension cable with the Live and Neutral wires reversed to correct any reversed supplies. Mark it to remind you what it does!