Malian musicians, I am told, mostly sing in a local version of a Mandika language called Bambara, which would be comprehensible to my Senegalese student, since Mandinka is a common third language in Senegal, after Wolof and French.
It was the musical phrasing and vocal techniques of blues that sounded Malian, not the lyric.
I don't think it it PC thinking that is skewing history. Rather it's the fact that you are basing history on the existence of recorded music.
If recordings were made by a true random selection of the population, and if sound recording had a history two hundred years longer, it would be reasonable to base an analysis of musical history and trace influences that way.
But the USA has been a racially segregated society for a lot of it's history and access to recording has not been equal. It would have been far easier for a white performer to record an imitation of a black singer than for the original artist to get his performance on disk (or tape or Wire, or even in a notebook, since non-standard scales and swung timings were a closed book to most manuscript-based classically trained musicologists).
You may have heard the quote from Ahmet Ertegun that when he asked other record companies what royalties he should pay, he was told "We don't pay no royalties to n******!" (Check the story of Danny and the Juniors or Soloman Linda too)
University-trained music historians are famous for the short range of their hindsight. They told me that all music started in around 1300 AD!
All the evidence is circumstantial, either way, and the topic is a weapon in the political armoury of both left and right.
The point I would make, as a card-carrying Liberal, is that the cross fertilisation of African, Native American, and European musical influences has generated the music that I love, and will be playing tonight.
There'll be some good Rocking tonight! (and Reggae, Blues, Country and Cajun, maybe even some folk!)
Cheers
Dave