Possibly, but I know too little about US sport followers to be sure. However, the one important aspect with some Italian supporters groups is the organised right wing element involved. The same is true in Spain, although maybe to a lesser degree.

Some of the 'ultra' groups are little more than political organisations and very well connected in some cases. The police do not seem to have had the powers or, on occasion, the desire to deal with them.

Italy (& Spain) have recent histories of very right wing leadership and neither country made the efforts to ditch fascism after the war in the same way as Germany. I'm not suggesting that either country is a fascist nation, but there remains a groundswell of fuzzy support for the right that can be indulged by young men via football.

British football hooliganism (now and in it's heyday) was associated with the right wing, particularly the National Front. Nevertheless, the recent history of the UK has not easily lent itself to accommodating active right wing extremism on the scale seen in Italy.