to put things in perspective the NBA finals averaged 19.94 million viewers in 2015 (and that was the highest since the MJ era) the 2015 super bowl had 112.2 million viewers that's over 5.5X more viewers for the super bowl. The thing that the super bowl has that no other sporting event has is the party aspect. You get non sports fans that watch one sporting event every year and it's partially for the commercials. A WC final with the USMNT could beat almost all US sporting events, but it wouldn't get half of the numbers that a super bowls does. There just isn't enough time to plan the parties.