These are important points, but my impression is that football in the US (leaving aside immigrants for the moment) is still seen as a "nice" sport to play for the middle class and for women. You won't get the hunger you get from (mostly) black sportsmen in American Football, Basketball etc. Or even tennis. The problems the league has suggest that when it goes up a level of seriousness then it hits a wall. The people who care about football (in the way the English or, say, Bengalis in London do) doesn't seem to have grown much.
I agree completely that the white US players are remarkably good considering and that the Hispanic/immigrant players could make them even better in the next few years.