Why is soccer so popular around the world except in America? (By which I mean "United States of", not "South America" or "Central America" or "Latin, sombreros not togas, America", or the dreaded Canadia. No one really knows what is popular in Canadia, since there's too much snow on the ground for them to play any sport not involving a puck) It seems this question comes up every four years during the World Cup, when everyone from Koreans to Africans to Danes are glued to their televisions and wearing their national team's colors, while Americans wonder what the fuss is all about.
The popularity of soccer is in its simplicity--it is the easiest game to explain to someone. Consider this:
Baseball--one team's in the field, the other team is at bat. The team in the field needs three "outs", each of which can be gained by the pitcher throwing three "strikes" into the strike zone without any hits, and a foul counts as a strike except not the third strike, or an out can be had if the batter hits the ball into the air and the field team catches it before it hits the ground, or gets it to the base before the runner or tags the runner. After three outs, the field team gets to bat, and this happens a total of nine times unless a tie in which case extra innings.
Football--the team with the ball has to advance the ball by running with it, or throwing it to an eligible receiver without dropping it, but the passer cannot throw it after he crosses the line of scrimmage which is the line on the field where his team started the play. The team on offense has four tries (downs) to get the ball at least ten yards, after which they get another four tries, eventually hoping to reach the defense's end of the field for six points. If they don't make it in four tries, the other team gets the ball, but usually after three tries you can punt the ball to the other team to give them worse field position, or try and kick the ball through the uprights for three points. You can tackle or beat the hell out of anyone carrying the ball, but don't get too aggressive because the referees are a bunch of Nazis about that.
Soccer--each side tries to kick the ball into the other side's goal.
See? Simple. And remarkably easy to play. If a bunch of kids want to play baseball, they need to get a bat, ball (maybe several because these get lost easily) and enough gloves for all the fielders. Then they need bases, and probably protective equipment for the catcher, and the name of a good glazier for all the windows that are going to get destroyed. For soccer? Just one ball.
So that explains why soccer is the most popular sport outside of the United States--but why isn't it more popular here in the U.S.? That's because we like to be different. It also explains why we haven't adopted the metric system either.