Peter, people around the world come to America to live, work and study, so to understand America in terms of its cultural differences is very important.
I couldn't agree with you more, Jack. Americans are much more assertive than most foreigners. For example, Americans begin a discussion with a focus on accomplishments and concrete facts.
You're right. America is a rather individualistic society, with less social pressure to conform. So you will need to become more assertive and to speak out on your own behalf.
Another aspect of American behavior is Americans are more guarded about personal space. So when you are talking to an American, don't stay too close. This personal distance is not due to body odor or bad breath, but because closeness lends a sense of intimacy that is out of proportion to the relationship at the moment.
Yes. Also, try to avoid physical contact while you are speaking. Touching is a bit too intimate for casual acquaintances. So don't put your arm around their shoulder, touch their face, or hold their hand. Shaking hands when you initially meet or part is acceptable, but this is only momentary.
In many cultures, eye contact is a sign of disrespect, which is not the ease in America. In fact, it is an indication of openness, honesty, and enthusiasm.