I don't think Americans are ignorant of the sport. It seems that most of us under the age of 50 have played this game at some point in their life, even if it was as a kid in games without much strategy and skill involved.
I think it lacks popularity for some of the same reasons that hockey is less popular than American Football, Baseball, and Basketball. And for a lot of other reasons.
Americans will never be passionate about futbol because of:
-Low, or No scoring games which often end in a tie, and even worse, are ALLOWED to end in a tie instead of OT or a shootout for every game, not just the final games in a tournament or playoff.
-Games that end with the victor winning by a single point, and often that difference being somewhat arbitrary, and not because one team truly outplayed the other
-Inconsistent penalty assessment. The laughable theatrics of rolling around on the ground wincing and crying are not really the fault of the players, because the free kick they are granted IS a valuable advantage. What is needed is a penalty box, and the resultant powerplay. And controversial calls should be video reviewed so that if any player fakes their injury (as in having NO contact and acting if there was a heinous assault committed) then THEY go to the penalty box (for an even longer time than a player would be penalized for an actual infraction). And if a player does this more than once in a match, then send the goalie to the penalty box on the second "fake" injury. It would put an end to the theatrics immediately, because the faking would have a serious cost.
- Yellow and Red cards......eliminate these. It is absurd to have a penalty that affects a team in a subsequent match against a different team, because it gives the next opponent team an advantage in their match that they did not earn in any way. Limit all penalties to the match in which they occur.
- Not having a game clock. Have a large visible game clock, and have a referee impose a time out to stop the clock for real injuries when they happen. No more arbitrary added time at the end, where none of the players or fans know when the end of the game actually is. Have 90 minutes end when the clock hits 00:00.
- The offsides penalty. Eliminate the offsides penalty. This would add offensive advantage fairly to both sides and increase the number of goals.