Re: If American Football wasn't called "football", would it be more popular...
The #1 reason is that its too complicated and has too many players, you really have to invest a lot of time into it to know what's really going on, the formations, the strategy, the details, the execution. You could say the same about other sports, but football goes deep. For the people who are really into it, I can see how they think that no sport is comparable. It is a re-enactment of war.
Personally, I love it. Best genetics in the world, no other sport can compete, not nba, baseball, soccer, rugby, boxing, mma, australian rules fb, hockey, etc.