why is american football the most poplar sport in the US?

There are many sports that are closely followed by Americans.  However, the most popular sport is Football.  Football is popular because it is fast-paced.  You have 11 players on each team who are in full-motion at the snap of the football.  Football also has a defined start and end time.  Unlike baseball, golf or cricket, football is timed with a clock and a winner is realized when the clock runs down to zero.  Football involves contact between players on opposing teams, and the contact can sometimes be violent as players collide, sometimes at full speed.  This contact creates an excitement and uncertainty among the fans, as you want to see what will happen on each play.  Finally, football is enjoyable to watch whether you are in person or watching on TV.