Stereotype of American of Students of a middle school

I work part-time at a academy, where middle school students come to study. I asked them to tell me about their thought of American and the reason yesterday,  good things or bad things. A student told me that American looks rather fearful. He told when he watch the American movie, he can always look at many scenes in which ators use guns and are on drug.
So I told them that such scenes are a way to attract the audience and earn money and not every aspect of America.
A girl student told me that American all looks rich and handsome and pretty.  She also told that American culture focuses on individual free, so they tend to only think themselves. Some students wanted to be American because westerners have good body and height. Through this conversation, I realized that children tend to more look at others' appearance than inner character.