Here are a few simple statements about fan interest in watching sports:
1) If you don't understand a sport, you're not likely to enjoy watching it for more than a few minutes.
2) If you don't having a rooting interest in a game, even if you understand it, your interest in watching it will be low. I know football well, but I never watch CFL games, because I could care less whether Rough Riders or the Allouettes win.
These are more important factors than the factors cited above, such as the flow, strategy, or other details of the games themselves.
We can all critique soccer, hockey, lacrosse, etc, and even baseball, football and basketball. But the reason most Americans can't watch soccer is that they just don't care who wins. Ratings for soccer go sky high when America makes a run in the World Cup because viewers have a rooting interest for once. But there is virtually no carryover; two weeks later, 95% of those watching America in the WC have zero interest in watching an MLS or EPL game, because they could care less who wins.