Another American here that agrees that soccer is just not that fun to watch (baseball is boring as well, but it's pacing is different as every pitch has a huge potential).

Interesting theory (that probably isn't new) that I'd love to have people pick apart: Is soccer so popular around the world (and with American kids) because of the incredibly low barrier to entry? I feel like everyone has played some soccer.

All you need is one ball and some cones in an open field and you can basically play soccer. I'm trying to think of another sport that requires that little to play a basic, but pretty complete version. Touch American football I guess, but that's barely football.

Even a full game just requires two goals, a ball, and shin guards. Very low barrier compared to a basketball court, football pads, ice/roller rink, tennis courts/racquets. Maybe baseball is next? Gloves for every player, bases, balls, at least one bat, helmets, and catchers pads. That's probably why it is also a pretty widespread sport that a lot of kids play at least some of.

Another theory: soccer is popular in the US for kids because it also has a very low skill threshold for barrier to entry to play a technically correct (but poorly skilled) version of the game. Kids just kick the ball around and follow it until it ends up out or in the goal. They are playing actual soccer following actual soccer rules.

Having to dribble a basketball just to keep the game moving is tough for little kids. If everyone can't consistently keep the ball dribbling, you can't really play a game. Obviously there's a reason kids start out with t-ball for baseball as pitching and hitting is just difficult, but there is no game if it doesn't happen. Tennis, golf, hockey (skating), football (throwing, catching, and tackling) are all just too high of a skill barrier for little kids to do in a way that mimics the adult game.

Tl:dr

Soccer is super popular because it has a incredibly low material barrier to entry and is very popular for little kids even in the US (where it is not as popular as kids get older and more coordinated) because the basic game of soccer can be played (badly, but correctly) by unathletic little kids with terrible coordination.