On my travels around the world I always run into way more German tourists than American. Yes, it is anecdotal evidence, but in Germany (and a lot of other western nations) it is encouraged and almost expected for 20 year olds to travel to other countries & cultures.
The reason I bring up German backpackers in particular is because there were SOOOO many Germans in New Zealand and Chile.. There were even more Canadians & Czechs than Americans.
Anyway, it's anecdotal, but a couple Americans I've talked to have agreed with me that Americans prefer to travel .. in the U.S. as opposed to exploring foreign lands. It's a generalization, but on average it seems to be true.
Germans are literally everywhere.
LITERALLY.