You do rude things like making slurping noises when you eat noodles. But there are also more internal differences. Japanese culture tends to place the group first. American culture emphasizes the individual. Thus, oriental culture stresses loyalty, filial piety and obedience.
American culture stresses honesty, integrity and creativity.
Essentially, these difference stem, I think, from the difference between Confucian culture and Judeo-Christian culture. Confucius taught that filial piety is the first and highest duty, and that from this, all other duties flows. But Jesus taught that we should love God even more than we love our parents. He even taught us to deny and hate our parents in order to follow him. A few weeks ago we heard a sermon in this church from a distinguished UTS professor who stressed that filial piety is the supreme value.