Bringing this back up. I noticed something was off with my rear bumper the day after I picked it up new from the dealership. Between the time I picked it up and the time I noticed the crookedness, it was only parked inside my garage and there was no chance anything impacted it. The left side of the bumper looks pushed in about a half inch toward the middle, and the right side is angled down more than the left.
I removed the bumper from the hitch structure that bolts to the frame, whereupon it was clearly obvious that the hitch member is not symmetrical. There bumper bolts to extremely thick stamped steel pieces that the hitch crossbeam is welded to. The stamped pieces were just made wrong, somehow. They are made from super thick steel, but the bumper is made from very thin sheet metal. There's no possible way that you could bend those thick hitch plates without completely mangling the rear bumper in the process. There's no evidence of any kind of impact anywhere on the bumper.
I'm having the dealership look at it on Monday. I'm nervous that they will try to tell me "oh somebody must have hit you when you were parked somewhere, sorry". We'll see...
Has anybody else gotten a crooked rear bumper on a new truck?