I recently moved to a "bad neighborhood" and was very surprised to learn that there was only one murder here last year, and it was between friends who had stolen something from each other. There were only around 13,000 murders last year in the US, a number that used to be more like 26,000 during the crack epidemic 30 years ago. US population has increased by 10s of millions since then, but murders continue to drop. A…
Even in Brazil I bet a lot of this happens in communities, where they can try to justify violence due to some perceived slight.
And of course let's not forget that America's crazy gun laws are pushed by gun lobbies because they help increase sales by creating an easy way to funnel guns into South and Central America.
Much of the violence is there because of things like The School of the Americas and the work of US interests in promoting less democratic states to make it easier to gather resources (see the book: Confessions of an Economic Hitman). While it may not be directly related to the gang violence, those policies do spill over and make this sort of trend easier.