Which ones are you considering? Some only provide surge protection and the better one also provide high/low voltage and frequency protection along with a myriad of wiring faults (open neutral/open ground/polarity issues). Whether or not they will protect from
all surges is doubtful (in my mind), but a campground wiring problem (esp. low voltages) is a real threat making the device worth every penny. Also, I see no way any surge protector will actually cause damage and I worked as a power plant engineer for 30+ years.
FWIW, I have the Progressive Industries EMS-HW50C (see below) and it has protected my A/C units many times on low voltage at some of the older campgrounds we have here in the northeast.
EMS-HW50CLou
05 Travel Supreme Envoy