Hmm, in North America they usually don't;

- Most and the best off grid ones are first come first serve, and there's no one to check you in anyway

- Some popular ones in National Forests can require online reservations (you can tell them you're Elvis, and pay with anon debit card)

- I was asked real ID just once, it was more a trailer park setup (I think that's more common in Europe too)

- In that case, driving license from different country helps a bit.