An other big deference that i see USA sports fan vs European sports fan, is that Americans sees the sports as a pure show.
Depends on the sport though. NBA has become much more of a show over the years as they work to attract casual fans that can afford to pay the ridiculous prices of tickets. American football also charges astronomical prices but there is a huge demand for tickets and the fans are likely more "die-hard". It's possible that the most committed fans of NFL/NBA/MLB are the ones that are priced out of going to the games.
"Well, no ones gonna top that." - http://tinyurl.com/noigttt