I played soccer from when I was five up through high school.
Personally, I found it extremely fun to play; a lot more fun than playing football. However, to watch, it's horrid. There is NOTHING exciting about soccer, it is easy to reach a level of skill that negates any realistic expectation of being fun to watch.
Why? Because people can kick extremely fucking hard. It's simply not fun to watch people kick a ball from one end of the field to another constantly -- especially when someone can do it in about a month or two of training their legs.
Now, dribbling, diving, headbutts, etc... that's where you separate the real talent, but these are not the primary means of playing the game: the primary method of play is kicking, which is, largely, talentless and boring to watch. Not to mention, like everyone else said, all people do is try to put themselves in situations where a ref will call a foul on someone else, try to cheap shot other people when a ref isn't looking, do what they can to get away with whatever illegal gameplay they want, and be constant egotistical assholes on and off the field.
The 150lbs pussy soccer player screaming at the top of his lungs is nothing more than an annoyance and a disgrace. Unfortunately, this describes 90% of all soccer players. Americans want to see badasses that can do things other people can't do -- and see them pitted against other badasses that can do things other people can't do. Nobody wants to see "talent" that's achieved with a few months of training. Additionally, nobody in America wants to watch a sport where they could kick the shit out of everyone playing it because they're 150lbs pussies that constantly bitch, cry, and scream on a field. We want to watch sports where the ATHLETES have the ability to lift us over their head with one hand while simultaneously breaking our back.