You said it runs over to the wall. Can you see where it goes from there? Does it go underneath or behind a cabinet? If you can get into the wires over at a cabinet or something and cut the wires there you may be able to see if the fault is before or after that point. Just say the positive wire is pinched in the bedroom ceiling area, if your light is mounted by any metal frame work you may be able to ground the light there and use the negative wire as the hot by moving it down to the positive where you cut into it.
I know you said there's nothing else on the circuit but did you follow that green wire which you say is positive all the way back to the fuse in the panel? I'm not saying it can't be but it seems like there would be more on that circuit than just one light in the bedroom. I say that because it's just so common in an RV that they try to run a whole bunch of stuff not single things because they're cheap.
Now let's say that you find after cutting into the wires down there that the problem is for word of there. I would then go in to the Power Center and see if you can identify those wires. Just say you found a green and white in their sheeting and you assume them to run back to the light. Now you could remove the ground right there and you have the light disconnected so as long as that wire isn't feeding anything else you would have Tsum there should be no ground so you should be able to check that wire for continuity to the frame if there is none you could make that wire positive and send it back to the light by passing the pinched green wire that is forward of your cut.
I'm speaking on my phone to put this in here so I hope it's not confusing
