Disproportinate representation of US culture? Which culture do you think should be represented in Hollywood?
From where I sit it's mostly a lowest-common-denominator approach that's designed to be inoffensive, appeal to the broadest culture possible, and sell the most tickets.
For example, in the recent Welcome to Marwen film, the attackers are all white, and one has a neo-Nazi tattoo. In the real incident the movie was based on, one of the attackers was black, and none had neo-Nazi tattoos.
A second example is the invented racist fix in a boxing match, where, again, the white boxer is shown as unfairly being selected as the winner of the match, despite incompetent compared to the black boxer. But in the real fight, most everyone, including the black boxer, agrees the match and outcome was fair: https://en.wikipedia.org/wiki/The_Hurricane_(1999_film)#Laws...
In the case of historical movies, this bias is easy to spot (except when it comes to the selection of which parts of history to show). But in fictional stories, it's harder to complain, yet the narrative pushing is just as strong.
I wonder if the writers of penny dreadfuls ever tried to 'improve' the public in some way. There's probably a sociology paper in looking at older pulp fiction or movies made via the old mass-production system to see if they are aimed in different ways than modern ones.