AC doesn't go to the trailer or vehicle battery. If it did (accidentally)
the battery would boil, foam and maybe explode.
Unless all you have is a popup that has a regular 15 amp plug that is
plugged into the 15/20 amp outlet in the pedestal, and that outlet is a
GFI or its breaker is a GFI, there is no GFI protection for RV power
supply from the pedestal.
GFI is used only to protect individual circuits (we're not dealing with
industrial GFIs).
Al