Just wondering how you would come to that opinion. Do you have first hand knowledge? Or just following conventional wisdom?
I once bought into that stereotype but I kept hearng annecdotal evidence to the contrary so I asked several non-americans their opinions. Without exception, they all repeated something like this (which I happened to save):
"For the most part, I've not run into that many offensive americans, despite the stereotypes. Americans who travel the world aren't your typical fat ass, mid west type folk. Well the ones who travel to more exotic places other than italy and england.
Without a doubt, the worst tourists in the world come from Japan. Pushy, closed-off weenies."