Recently, I corrected someone as to whether African Americans are predominantly derived from Bantu speaking or non-Bantu speaking regions. Since the traditional historical sources suggest a bias toward the West Africa, from the Yoruba kingdoms all the way up to Guinea coast, the majority of the ancestors of African Americans would not be of Bantu identity. This West African bias is reinforced by books and movies like Alex Haley's Roots which tend to fix the place of ancestral origin in places like Senegal, as well as the perception of some that African Americans were Muslim before their arrival to the New World¹ (since Islam tends to be most common on the Western and Eastern antipodes of Sub-Saharan Africa). Nevertheless, there textual evidence for the importation of slaves from the Kongo coast in Central Africa (this is the dominant source in Brazil).

So, it was with some interest that I stumbled upon this paper, Charting the Ancestry of African Americans. The gist of their results are that "We show that >55% of the U.S. lineages have a West African ancestry, with <41% coming from west-central or southwestern Africa." The sample size was large, with over 1,000 African Americans, and 5,000 individuals from all parts of Africa (including North, East and Southeast). Of course, this is a survey of maternal lineages. Interestingly, the authors end with this caution:

...Even with greatly improved geographic coverage, it remains the case that many mtDNAs are very widely distributed throughout the African continent, most likely as a result largely of the Bantu dispersals (Salas et al. 2002), but no doubt also as a result of both earlier and more recent movements, including those that are due to the Atlantic slave trade itself (Salas et al. 2004)....
...
Considerable caution is therefore warranted when dealing with claims in the popular media (such as the acclaimed and prestigious BBC television documentary Motherland: A Genetic Journey, first shown in the United Kingdom in 2003) and those made by genetic ancestry–testing companies about their ability to trace the ancestry of certain American (or, for that matter, European) mtDNAs to a particular locale or population within modern-day Africa. Our analyses stand as a warning to unsuspecting members of the public who may be seduced by such promises.

1 - There is a problem with the contention that African Americans were Muslim prior to enslavement, and that is that wide scale Islamicization in much of West Africa, even places almost uniformly Muslim today like Senegal,is a feature of the 20th century. The key is to remember that Islam tended to be localized in urban trading entrepots like Timboktu and among the traditional elites. Though some Muslims were enslaved and brought to the Americas from Africa (this is historically attested), I would be willing to bet that as many Muslim Turks and North Africans were brought over as Muslim blacks ("Turkish" slaves were apparently a presence at Jamestown, that is, slaves of Muslim origin who fell afoul of Christian pirates and were likely sold to Italians, not necessarily native Turkish speakers).