The "root" is probably in the police, war on drugs, racist people on positions of power, neglected neighbourhoods, etc. The World has been trying to solve racism for decades now, if it was so easy, we wouldn't be talking about this right now.

Affirmative action makes sense because it's a policy that's simple, cheap and fast to implement to counterbalance this. And let's not forget that, in the past, the State legally discriminated against those people and no historical repair has ever been given.