You may be correct that the converter is hard wired but in most smaller RV's the converter is plug in. If I am understanding your progress so far, you have power to the campground box or pedestal. I will assume that the converter is on its own breaker in your camper. Turn off all the breakers in the RV and turn the campground power on the breaker should hold. Then turn on each breaker in the RV with the converter being the last to turn on. Does everyone hold or just the breaker for the converter cause the campground breaker to trip? Is the breaker for the converter a ground fault type breaker or is there a secondary ground fault type outlet somewhere else in the RV that may be on the same breaker. If there is an outlet type ground fault make sure that if has not tripped.
The campground breaker may also be bad or weak, is there another power option close by were you can plug into to test this? Campground breakers fail quite often.