The Heart of Darkness these days is Harvard Law and Yale Law.
Its a shame that the Nigerians or anyone else does not deluge these law schools with missionaries.
The entire United States, not merely the schools you cited, is "post-Christian" now and is recognized as such internationally and viewed as a fertile missionary field, so much so that several countries are sending missionaries to the USA. I work in Fullerton, in Southern California, and there is a huge and growing presence of expatriot South Korean Christians there for that very purpose.