Marko i hear what your saying, its a pretty complex issue with no one reason, its many reasons why things happen.
Ground zero for black culture and intellectual thought in North America is in Harlem or NYC in general, what happens there ripples outward and effects people here. There has been many things that have undermind the efforts of positive people in music and the community for example - the positive political hip hop music in the late 80s early 90s where blackballed , the artist lost control of the music and the major record companies dictated what direction the music would head in. So money, pimp gangster was promoted while the real artist had the doors shut in there face.
Another example- crack hit the communities hard in the 80's and 90's , drug us sky rocketed which came from people outside the communities, at the same time Ronald Regan excellerated the so called war on drugs which is really a war on poor people, a war on black people and other visible minorities. You then see the mass privitization of the prison system creating a profit making business based on how many people you lock up so you have the businesses lobbying for harsher drug sentences, they where seeing dollar signs. Police brutality kicks into over drive creating a miss trust between the black people and the police which are now seen has aggressive authorities coming to the hood which is just picking grounds for the prisons to herd people into the camps called prisons. When the poor people get out of prison they become really bad people creating a viscious cylce of violence and crime that gets exported everywhere.
The drug war is a war on poor people plane and simple. with around 2 million people behind bars in the states, a huge portion are in there for non- violent drug offences. Then when you get out of prison you cant get a job cause of your record, and you cant vote for anyone in power that will listen to your cause, your screwed .