My opinion is that advertisers haven't figured out how to advertise on soccer.
FIFA doesn't help much in this regard... from the FIFA Interpretations of the Laws of the Game:
Commercial advertising shall be at least 1 m (1 yd) from the boundary lines of the field of play.
No form of commercial advertising, whether real or virtual, is permitted on the field of play, on the ground within the area enclosed by the goal nets or the technical area, or within 1 m (1 yd) of the touch line from the time the teams enter the field of play until they have left it at half-time and from the time the teams re-enter the field of play until the end of the match. Similarly, advertising is not permitted on the goals, nets, flagposts or their flags and no extraneous equipment (cameras, microphones etc.) may be attached to these items.
I don't think advertisers haven't figured it out, I think that soccer does not fit the US model of sports advertising. Many major companies are marketing at soccer games. Samsung is Chelsea's shirt sponsor, Emirate air lines sponsor Arsenal (I think they are owned by the same person), AIG paid huge change to sponsor Man U (which by the way is owned by the Glazers, the same people that own the Tampa Bay Bucs). Twelve of the 16 MLS teams have shirt sponsors.
As for money, here are the value (in $ billion) of sports franchises from Forbes for last year:
1. Manchester United $1.8
2. Dallas Cowboys $1.6
3. Washington Redskins $1.5
4. New England Patriots $1.32
5. New York Yankees $1.3
6. Real Madrid $1.29
7. Arsenal $1.2
8. New York Giants $1.18
9. New York Jets $1.17
10. Houston Texans $1.17
6 of the top 10 are NFL, 3 are European soccer clubs, and one is a MLB team.
So, someone has found a way to make money from soccer.
The US just placed a bid for the 2018 and 2022 World Cup Tournaments. The soccer environment here will be much different than what it was in 1994, when the US hosted the World Cup.