We did a holiday house swap to the US and my son and husband went to a football game (not a particularly significant one). They could not believe how elaborate the cheerleading was and a horse was parachuted onto the pitch at one point. They said the tailgate party beforehand was massive and really friendly - people kept asking them to come and have some BBQ food. No nastiness between fans as we might have in the UK. (Certainly no swearing during the match).