Tully Mars - You don't know what offensive behavior is until you are on a slow elevator full of French tourists in the summer.
Some things can't be unsmelt.
I had a cousin who was a park ranger and he several times had to stop European tourists from trying to pet the bears.
While I'm sure, due to a lack of interactions with a lot of other nations for the average citizen the average US tourist is worse, I think being an ignorant obnoxious tourist is one of the planets universals.