Don't forget about the actual playing time. Soccer is non stop for 90 minutes. American Throw and Catch (as an Irish friend once put it) is a lot of standing around, then they run a play that lasts maybe a few seconds, take a two minute timeout for TV, run another few seconds, stand around some more ...
I love the NFL (live 6 miles from CMGI field) but the average play takes 4 seconds.
You film an entire game of active plays into 12 minutes.
Good points. Also keep in mind that NFL football players are unable to play both sides of the ball: when possession changes, all eleven players go to the sidelines and are replaced by another eleven. Wide receivers are too wimpy to play defense and defensive linemen are too slow to play on offense. And don't forget special teams--the starters can't be bothered running punt or kickoff coverage.