US Football, baseball, basketball and hockey aren't the main sports there ?
Which one of the above do you leave out ?
I'd say A. Football, baseball, basketball are the main sports, nationally. 4th is hockey (minor but hardcore), and distant 5th is football.
As far as simple attendance (b/c basketball, hockey attendance is capped due to the arenas) football has passed hockey and basketball. But the biggest difference is television $$$, MLS is still waaaaaaaaaaaaaaaaaaaaaaaaaay off for ratings and tv deals. The positive thing is that many people still haven't "discovered" the local league yet, or many are more ethnic types that follow their country's league. So it might take a while but there's nowhere to go but way up.
And if USA ever makes it far in a World Cup, or hosts another, the push will be even faster.
So you have solid 20,000 attendance at most matches, but they still need to translate that to TV $$.