Now neither the green (ground) wire nor the neutral (white) wire is
connected to the trailer frame or shell.
The old way could be dangerous if the RV park wiring had reverse polarity
or other defective wiring or connections. This situation would make the
trailer shell/frame 120V to ground. Also reverse polarity would connect
120VAC to one side of the 12VDC wiring, which if they were connected
correctly would make the shells and plates of the cigar-lighter type 12V
sockets "hot."
A separate ground strap from the trailer frame/shell to a good dirt
ground is a good idea. My '79 Silver Streak has one.
Al