I mean, the racism in some ways is deep rooted in some of the club supporter groups. They've been radicalized and how they are has existed for a long while now. But some of it has changed recently, and the differences are two fold. one, there's more media exposure to draw attention to people behaving badly. Secondly, many people who might have been limited, or shunned, or frowned upon by committing acts that are seen as poor, feel emboldened to do these things. People feel like they're ok shouting things at football matches that at some point they weren't allowed to say or do. Some of that also relates to some of the changing attitudes. Saying some things are not ok now. I also think in some ways, you've seen some of the demographics of who attends football change. As ticket prices have gone up, you've seen some of the lower classes, along with potentially immigrant groups be priced out of attending matches. Tickets are also controlled by the same groups, and in many cases passed down to generations, so they don't have exposure to new fans. The isolation does breed a familiarity and resentment against the other.
As for why it's not as prevalent in North American culture, it certainly is. It's just somewhat been sanitized or limited in scope. If you don't think it has happened in droves in college football games or basketball games or whatever, you probably have had your head in the sand. I do think though that some of the differences in someways are the fact that the US has long gone through much of the growing pains of needing to overcome integration into sports, and went through much of it in the 1940s (and in college sports much earlier). Sure, there's still some issues with it in some areas, and the racism is still there, but I think some of the explanation as to why it's different in Europe is there are many places in Europe where they don't have a lot of diversity. There are parts of the US that aren't very diverse, but athletically, every major sport (sans Hockey) has been integrated, and most to a large degree since the 1940s and 1950s. If you look at most of the major sports, there's really only hockey as the outlier that isn't dominated by non-white people. Basketball, Baseball, Football, Soccer, all of the sports are overwhelmingly diverse, many times not reflective of the populations that they exist in. If you look at some of the rosters of European football clubs, most of the clubs in smaller leagues, still really only have what are traditionally, white European players. If you go down your secondary or tertiary leagues, there might be one or two import players. Maybe. Heck, it's not that far in the past to where most of the English league rosters had just a few imported players outside of Great Britain. If you get beyond the top level or two, that's even more pronounced (although in England, there have been quite a few immigrants post WWII to increase diversity in sports). But many clubs have long been not a big location of diversity. And if they are, some of that drives some of the racism, because the player becomes the other. So combine what has long been a bit more radicalized, along with lack of exposure and integration, and you get people acting like idiots. But I wouldn't say that they have a greater problem than say in the United States. There are parts of Eastern or Southern Europe where it's a bit more prevalent, but some of that is related to having a greater rise of the far right, or feeling more stress of immigration. Racism isn't something one area has a monopoly on. But I think there was for a while (maybe it's less so of late) a greater taboo on doing things that are overtly racist in public in the United States. You maybe don't see the same society shunning in Europe that you did for a while in the US to overtly racist stuff. It doesn't meant that Americans weren't racist or didn't do things that were racist. But at least in the public sports arena, it was something that would see condemnation.
