Of the four major sports in the US, Hockey is the most agonizing when there's a rooting interest. The reason is the game goes with the foot on the gas for most of the time.
If you've ever watched playoff hockey with a rooting interest, you know what I mean. When the Sabres are in the playoffs, the whole game is spent on the edge of the seat, in anticipation of a goal. Indeed, goals come out of the nowhere in hockey, and that makes it even more interesting. In basketball, baskets come all the time. So the anticipation isn't there. In Football and Baseball, the anticipation is made for TV: full count with the bases loaded. 4th and inches. Those are edge of the seat moments, but when they end, the fan can go back to the whole seat.
In the sport mentioned above, we're often fans of the city. But the players on the team aren't us. The players on the Buffalo Sabres aren't from Buffalo (with rare exceptions). And while they represent Buffalo, they aren't Buffalo.
So now, if you're still with me, start with a rooting interest. If you're from the US, then you can root for your country. A rooting interest in the people from your country is what is cool about the Olympics.
Image via Wikipedia
Now, add in some real-world, built in rivalries. England v France. Spain v Mexico. England v Germany. US v Mexico. Argentina v Brazil. Algeria v France. North Korea v US. Many of these games won't happen, but could. Geopolitical tensions are present at Football matches. And this just adds to the rooting interest of fans.
England vs US, the colony that got away has a historical arc that puts Yankees Red Sox in an entirely different bracket.
So, you have rooting interest in countries with additional geo-political back drops that make the result that much more critical.
So here's where the edge of your seat comes back. Football doesn't stop for commercial. It doesn't offer the fan with a rooting interest a moment's rest. There aren't time outs (or TV time outs). Leave for a pee, and you might miss a goal.
And while people in the US point to the lack of goals as an indictment of the game, it's the potential of a goal that makes the game great. Not the goal. The goal is the release of tension. The build up to a scoring chance is a built up to tension. That goals are rarely scored underscores how much tension gets built.
That's why people love it.