I believe there's several reasons for the media's wholesale neglect of African coverage. First and foremost news media is a business. They may try to claim otherwise, but it is. Money pays for the operations needed to cover the stories. And the media consuming public in the western world can't identify with the happenings in Africa and therefore don't watch or read about. Whether this is racism or ignorance is immaterial. They just can't.
Second, news media has this obsessive 'me too' attitude. If one outlet covers it, then they all have to. Often this happens to the extent that all they do is rerun the initial story verbatim.
Third, due to business decisions, there is a serious dearth of reporters in Africa. And this is compounded by the fact when one does get there to cover a story, it's probably a low level reporter who has little or no knowledge of the region, culturally or linguistically.
And fourth, in the case of the Paris attack, the story is about one of their own. The terrorists might as well have attacked CNN or CBS. This 'stand by your brethren' is no different than what we saw with New York City cop killings when a nation of police rallied in support.
I wish the situation was different, but unfortunately it's not and I don't have a solution.