As an electrical engineer and pretty experienced motorhomer in more than 20 countries, I guess I should know better but I have given up worrying about "reverse polarity", presence or absence of an earth, or whether the campground circuit has fuses, circuit breakers, earth leakage breakers or whether they or the ones inside of my vehicles are single pole or double, or whether there are 35 RVs plugged into a single circuit or if there are 6 French MHers daisy chained off my extension reel or any other combination or permutation.

Standard accessories for any American RVer.

Looks good but no earth and no useful overcurrent protection

(Not as bad as it looks because there is no earth conductor to the power outlet anyway.
When I went to bed there was just mine plugged in, but by morning the power board was getting a bit crowded.
Mine at the top, an Argentinain's in the middle and a German who just crossed from Chile and who was having adaptor problems on the bottom.
We all lived through the experience)
Lots more "amusing" photos like these
The only really safe system would be to have a double insulated multi-voltage switch-mode
battery charger installed in a separate insulated compartment and use that to charge the batteries and act as a power supply to feed all the 12V circuits and an
inverter that supplies essential mains appliances on board. A small on-board generator - permanently wired - could supply any big stuff.
That way it wouldn't matter too much what sort of hookup you were using because it can't compromise your fixed installation in any way..