You may be asked where you are from, what do you do, what do you want to do in Japan, what do you like about Japan ...
There may be some people who has some prejudices against Americans or all foreigners, but I think many Japanese do not judge you only because you are American, we see what kind of person you are, so please do not worry and enjoy staying in Japan:))
I think many Japanese are so kind to everyone who cannot speak very good Japanese;)