I don't think she dresses in a distinctive way, she just dresses like Kirsten Dunst.
I've been raised in the states almost my whole life, so I've gotten to know the culture pretty well, but I don't associate Americans with dressing in a particular sort of way. I think labeling something American is kind of ridiculous, as there are tons of trends and styles people have here. The same goes for Europeans.
People dress how they like, I don't think it has anything to do with where they were raised. If they like trends and like fashion in a way, style will be come to them no matter what.