What it means to be American?

So one of the journal assignments I had to write about was what I felt it meant to be an American.  Then, I needed to describe how I hoped to leave a positive impression on the Europeans about teenage Americans today.  Even though I have already turned this assignment in, I still think about the question.  Unfortunately, I do not think European cultures think about us as positively as we believe ourselves to be. I guess I'll find out in 103 days.  What do you think it means to be American?  What do you think it means to be a teenage American?