I saw a couple of overviews of religion in USA. The percentage of people who believe in god (Christianity) are significantly higher in the states with a bigger black population, and hence the states that had a big(ger) part in slavery. How did this come to be?
These states are more religious overall, but the black population seem to stand out even more.
More can be said about comparatives, but for the prevalence of Christianity in the African American community: Why didn't freed slaves reject Christianity? by u/uncovered-history
Why did Christianity remain so widely accepted within the African-American Community after slavery ended? by u/yodatsracist