en.m.wikipedia.org/wiki/Dark_Alliance_(book)Is the original expose about cia involvement with crack, and still I think a good starting place, even if it has some flaws. It was less about what crack would do to americans, (though they were completely apathetic towards the harm they were doing in the US) and more to do with what the cia wanted to do with off books funding that crack provided, secretly fund paramilitary deathsquads in Nicaragua.
I think if the CIA is still involved in US drug trafficking, and I wouldn’t be surprised, it is probably still for off books funding primarily.