There are some anomalies in US sports that do not exist elsewhere.
Firstly, that they have a very successful Collegiate system of sports which is dominated by Gridiron followed in it's wake by Basketball, then way down the pecking order is Baseball, Soccer and Athletics (in no particular order). At some of the more established US college's, the paying public (in attendances) for both Gridiron and Basketball can easily surpass that of it's professional cousin's. For some fans it's the collegiate versions of the game that they trust and love the most. Most College teams have been around longer than their professional counterparts.
The monies raised by the fee paying public in these primarily "amateur" gatherings (Gridiron/Basketball) along side TV revenue's is in some case's one of a college's major revenue streams and can be a multi-million dollar income stream.
Whilst the audience both live and for TV in the US is primarily with NCAA administered sports, it's the professional version's (NFL/NBA) where it can be argued the money is really at and that is driven by broadcast right revenue alone. The NFL have some of the most ambitious revenue streams and growth projections, especially in International markets in professional sport that make the eye's of some Wall Street type's water.
Baseball is slightly different where the MLB's collegiate cousin is a poor third behind Gridiron & Basketball in the numbers of students on scholarships, attendances and TV revenue, it's professional cousin is the people's sport with in general match-day prices to match, that can be as cheap as $ 5 per ticket per game. IF you've 81 home games in a season then you need to make it affordable for all. And has TV rights revenue's that some sports governing abroad would kill for but are dwarfed by those of the NFL and NBA.
So the question it needs to be is it a) participation, b) press coverage or a lack of it, c) financial clout/revenue d) bums on seats or e) History that makes a sport a "Major" or "Minor" in the land of the free and the home of the brave or beyond?? Discuss or javelin?