"I've never understood why American blacks are so fond of Islam."
I'm no expert, but my opinion is that they hear people say that Christianity is the "White Man's" or "Slave Owner's" religion, or that they think they're getting in touch with their African roots by converting to Islam. I don't know the exact statistics, but I think that most of the black African slaves imported to America were Animist (i.e. pagan)
Yes, I agree, it has to do with that "Mother Africa" thing. But the reality is that Muslims despised subsaharan Africans, captured them and sold them into slavery the way they did with any "infidel" group. (The great majority of those captured by the Muslims where Europeans, btw, who were sold into slavery throughout North Africa and other Muslim territories.)
Most Africans who were brought here were animists. In certain parts of the US, African slaves were forbidden to receive religious instruction and Christian missionaries were prohibited, so they weren't even Christianized until fairly late in some cases.
But I think blacks perceive this as a way of "getting back" at whitey, although it's a pretty self-destructive way of doing it!