Well it is soccer after all.
You've obviously never heard 100,000 people belting out the words to "Land of Hope and Glory " at Wembley Stadium, It's so loud the stadium vibrates and you can't hear yourself sing, or the non stop cacophony at Galatasaray, or Liverpool's Kop in full song.
American sports crowds are wimps by copmparison, Soccer crowds don't need organs, Marching Bands or Cheerleaders to bring tell them when to make a pathetic little whimper of "Charge". They sing in massed choirs with a varied repertoire and a a lot of wit.