I was in the middle of it in Germany in 06. It was beyond intense. At one point on the way to the game against Ghana in Nurnberg American fans filled up a train and some guy was banging his hand against the wall and then screaming every player on the roster's name and people were just going insane beyond name calls. When we departed the train it was like we were walking towards a battle.
There is no other sporting event in the world like international soccer competition.