FWIW, I attempted to replace a standard 110 outlet in the kitchen of our Jayco designer with one that had a couple of USB outlets. In the process, I discovered that the existing outlet was not standard in that there was no outlet box for it to screw into. Instead, it had a couple of 'wings' that fixed it to the hole cut into the plywood wood... sort of like an old work box would do. I thought about putting in a standard box, but the electrical cable was too short to easily attach into the back of the new outlet. Ended up putting the original back in place as it wasn't worth the trouble for me. Your situation could be different, but there's no way to know without opening up the existing outlet to see what you have.
2008 Jayco Designer 35RLSA pulled by a 2007 Chevy 3500 D/A SRW