American Football is all about something called the Line of Scrimmage. Think of a line drawn in the sand with two groups of men on either side. The two teams are essentially battling for possession of the territory on either side of that line. This is very warlike, dramatic and appealing to the American psyche.
The defensive mentality is two-part: 1. The other team is NOT going to cross this line, and we're going to beat the snot out of anyone who tries, and 2. If you do manage to cross that line we're going to be REALLY pissed and pound you even harder. The defenses primary responsibility is to hit people. Hit 'em often, and hit 'em hard. I can't think of any other sport where this is the case.
On offense it's only slightly different. They are going to do whatever it takes to move that line forward. Our guys are going to take whatever the defense can dish out and still push you back. Maybe one of our guys will run straight into your guys, and you won't stop him. Then again, maybe we'll just bypass most of your guys buy chucking the ball over everyone to one of our guys.
Finally, there is the spectator aspect of the sport. Coaches are MUCH more involved than any other sport. Therefore, you can be a fat American slob on his couch on Sunday afternoon and envision yourself leading a group of crazy young men to victory, without getting your bones broken, tendons snapped, or head ripped off. It's also FUN to watch a sport whose primary tactic is to hit the other guy as hard and as frequently as you can.
Diomedes