If something ever happened to a shore power cord itself, it'd be a dead short because it got damaged, in which case a 30 or 50 amp breaker supplying it would trip anyway by the instantaneous element in it. Unless someone tapped into the shore power cord, there is no possibility of it suffering an overload condition.
The sort of thing which is really ridiculous is the 30 amp to 15 amp adapters like this Camco 55233 because there is NO overload protection for a 15 amp extension cord above 15 amps.
I can just picture someone coming along and plugging one of these commonplace adapters into the other end of the cord to get 30 amps again.
