The answer is the Caribbean.
While Nigeria is a significant source of Black immigrants to the United States, it is not the largest. Nigerian immigrants are a substantial part of the African immigrant population, but they do not surpass the numbers from the Caribbean.
The Caribbean is the largest source of Black immigrants to the United States. Countries such as Jamaica, Haiti, and the Dominican Republic contribute significantly to this population. Historically, the Caribbean has been a major region of origin for Black immigrants due to geographical proximity and established migration patterns.
North Africa is not a major source of Black immigrants to the United States. The region is more associated with Arab and Berber populations, and its migration patterns to the U.S. differ from those of sub-Saharan Africa and the Caribbean.
Kenya, like Nigeria, is a notable source of African immigrants, but it does not account for the majority of Black immigrants. The numbers from Kenya are smaller compared to those from the Caribbean.