On any number of trips to Germany, I am almost universally thought to be German. I have a German first and last name, I am of German descent (second generation), and do not speak German. I only know enough phrases to say "I'm sorry, I don't speak German, do you speak English?"
Other countries peg me as American immediately.
In Japan, actions like blowing your nose and crossing your legs is a big giveaway. Also, I felt like a lumbering oaf in the way I walked compared to Japanese women -- most had very small strides compared to what I think is a normal American walk. (10 years ago, so maybe different now?)