Black Americans seem to have largely identified with Christianity despite many parallels between the enslaved Black experience and the Jewish tradition of Exodus. Harriet Tubman is even popularized as a Moses-like figure.
Was Black Judaism more prominent in early American history or has Christianity always been the preferred or imposed belief-system?
In this answer, I discuss why it would be exceedingly unlikely for Judaism to have taken hold in early US Black populations, though there WERE some Black Jews in the Caribbean/South America, enslaved and free. It was rarely due to a specific affinity for Judaism but rather due to their parentage or the conditions of their slavery.
In the US, the kind of Black-Israelite connection you note definitely took hold, and Black religion, even if Christian in nature, often had a definite tendency to emphasize the Old Testament; that said, organized American Black Judaism movements did not begin until the 20th century, as far as I'm aware. There were also Black Christian movements which, like some Christian movements still today, coopted Jewish ritual and identification while still maintaining fidelity to Christianity as well.