Japanese people are renowned for being polite. But I think "polite" is a misplaced word because in Western culture, whether someone is polite or not is completely optional. Some people are polite and others are not. The meaning of "polite" in Japanese culture is deeper, and perhaps a more proper English word to describe Japanese people is "respectful" of others. More than just being polite, being respectful implies an attempt to acknowledge other people's culture and ideas and an effort to not hurt people's feelings.
I think most Westerners leave Japan being a little more polite than we came, and maybe even more respectful of others. This comes through some rather rigorous training, however.
For example, when foreigners first come to Japan, we are met with a variety of unknown, unrecognizable food that most of us will at least try out of politeness. Even if we don't like the food, we may say we like it, out of politeness.