Probably that's why soccer is not popular in US. You can't interrupt soccer game for an ad. That's not the case with NFL, where you see an ad every time players stop playing.
From my experience the US broadcasts of soccer do have a ad popover the playing game on some games; often over or in addition to the scoreboard. It is much like an animated banner that you would get on a website. It does not cover the entire screen; but it is still intrusive.
Of course there is still exposure to the stadium side banners, and shirt sponsors as with all soccer games.