Well, congratulations to the USA for their win. England only managed fourth.
Roger, I can see why soccer would be popular with American kids. The only equipment you need to play is a ball. Then you can go to the park and use the proverbial jumpers (sweaters) for goalposts, and you have a game. It may last 20 minutes, or I've seen them go on all afternoon with people coming and going. There may also be the attraction of playing an truly international sport. The four that you mentioned are still predominately played in North America (although MLB played their first competitive fixture in Europe just over a week ago with a game in London). The USA women's soccer team can now say that they're the best in the world (again).