I cant tell if youre being sarcastic or not with your second statement.
I checked it up. Its hard to know for sure but according to fbi and us census data gang related homicides make up between 30 – 50% of all homicides. Thats a significant number you cant just not care about.
It really does not make sense to discuss european countries because of different nature of environment. We dont even want to have their criminal atmosphere, its very bad. So why bring proofs of countries that we dont want/ cant emulate?
By the way japan has pretty healthy ethical culture. They are hard working people, very family minded and extremely respectful as a whole. That must say something.