Hey there!

So, this doesn't exactly answer your question, but you'll hopefully find it really relevant. /u/Firedrops provided this amazing podcast for the AskHistorians Podcast project last year, and it discusses the history of Vodou and spiritualism, both in the Caribbean and on the American mainland.

I hope you find it of interest! :)

They didn't completely disappear, they were mainly just syncretized, although a bit differently than in other places. For example, in New Orleans, a place with cultural ties to Haiti, there are practitioners of a similar religion called Louisiana Voodoo. Although, New Orleans is not best example since it's history is much different than the rest of the US.

Hoodoo (sometimes called rootwork) is a completely different set of folk magic practices done by African Americans in the South which has a lot of African roots.

A lot of practices in African American churches also parallel African ones, like an emphasis on call and response and how "catching the spirit" resembles a trance like State that is central to many African religious rituals.