Yes, you can. It will provide additional safety should there, for some reason, be an "open" from your RV to the electrical ground. Should, for some reason, the frame of the RV come in contact with the hot side of your AC and there is not a ground, you could have 120 volt potential between the trailer and ground. I saw this happen at a camp ground many years ago. For some reason the trailer was not grounded electrically and the campers complained that they were getting shocked when exiting the trailer. Yes, I think if you can you should. It's better to be safe!