I thought there was some influence. I know the Irish R’s were dominant in American speech. But I imagine the plantation owners spoke a very high cultured English, and though the vowels were broadened naturally by the distance from England and the more pastoral /rural colony life, I had believed that the slaves’ accented English had an influence in the young children under their watch. Maybe even the rhythmic evenness of American English contrasted with the clipped British of today? Hard to say.
It would be foolish to count out the African influence in language since there was such influence in food and music. And I have seen so many little anglo toddlers here speaking with a Mexican accent our outright fluent Spanish thanks to their nannies.
“I know the Irish R’s were dominant in American speech.”
Don’t think that was true of the Virginia planters- Washington et alia prolly had the soft non-rhotic Tidewater accent. Kinda like this:
https://www.youtube.com/watch?v=1RzVKCWXrRA