That's an interesting observation. I don't have a PhD in sociology (thank goodness) but here's my guess as to why you don't.
One, there has to be a large population for the problem to be noticed. Putting aside white thugs for a moment, let's say that 5% of blacks turn to the thug culture. That's a lot of black thugs, in America. But Europe just doesn't have that many blacks in the first place.
Two, those other countries don't have the legions of race-hustlers we have. Those folks act as problem multipliers, making things much worse.
But here's something to think about. Europe is now approaching a critical mass of muslims. And their mosques are full of religion-hustlers. So Europe will have it's own analogous problem. Only theirs will develop into something much worse, I think.
The common thread is that sometimes, when people do bad things, they justify it w/an excuse. Per this thread, historical slavery is being used as an excuse. As you can see by the posts, many folks, myself included, don’t buy this.
The excuse is simply a diversion. To focus on the diversion and not the behavior is pretty absurd and a common propaganda tactic.
To say this occurred because of slavery only justifies this behavior. I highly doubt you would appreciate it if you got your butt kicked “because” of history.