I would have to say that the best part of American culture is the firm belief in the “American Dream” – if you work hard enough and want badly enough, you really can have or do anything.
The worst part of American culture is our total ignorance and unwillingness to learn about and respect other cultures/nations. Really, for being one of the biggest “melting pots” in the world, so many of us remain astonishingly (and, to me, embarrasingly) ignorant of other cultures and countries….