When you grow up in a soccer culture, you expect a certain "visceralness", a direct connection, from a sport. Everybody in the audience of a soccer stadium has played with a ball and a makeshift goal out of two cans in their youth, and when they watch a professional soccer game, it really isn't any different; it's just 22 guys who are really good at it, going at it with full force for 90 minutes.
In contrast, American Football, to a soccer fan, is a very "artificial" sport. It involves helmets and massive body padding, judges who confer video screens and replays, interruptions all the time, etc. etc.. There is no "men against men" aspect in AF, and I think a lot of soccer fans (including me) find that pretty unappealing.
Somewhat related, I always scratch my head when I see a group of guys playing touch football. It's clumsy, and gets nowhere near the real thing. Whereas a soccer game with 6 guys already has the same visceral appeal going that a 22-guys one has. So, I think that disconnect between low-level sport and high-level sport in AF is missing for soccer fans.
I see what you're getting at, but I actually have to defend football on this one. I did play football at recess in elementary school, so I have played the simple and visceral version of it. Offense meant a quarterback (which we took turns being) giving the ball to someone who tried to get it to the end zone. Defense meant trying to catch whoever had the ball and take them down. It was that simple, and actually very fun. And it may seem very far removed from professional gridiron football, but it actually isn't; it's just that in the pros the strategies have to be a lot more complex because the simple style of play really doesn't work reliably in the professional environment. This even goes for the stoppages - it's easy enough, in a three-on-three football game with simple strategy, to set up for the next play in two seconds without a huddle. When you've got 11 very large and very skilled players trying to stop you, and you're trying to coordinate 11 people on how to deal with it, the pause is just a lot more necessary.
In some ways I think the same does apply to soccer. I was the star of some childhood soccer teams, because I had good aim and good speed, and the coach could count on me to just be wherever the ball was and try to score with it. It obviously doesn't work that way in the big leagues, where teamwork is a lot more essential and relying on one player the whole time simply cannot work.
In every sport, more professional = more structure, I think.
A sprained ankle is the worst you can get from it really.
...
I must have grown up in a really rough neighborhood for soccer.