No, Afr. Americans are not the most influential of the African diaspora.
If Africa as a whole/singlular culture was rightfully accredited for it's advances and influences that it has contributed to the world since the beginning of time, it would quickly become very evident how the influence Africa has/had on this planet is almost immeasurable.
One could argue though, of course, that Afr. Americans are included in that "African influence" due to the fact that back then AA's too were Africans. But I'd disagree there too seeing as how AA culture is a world apart -and almost completely disconnected from-African culture today. We were at one time Africans, but the topic is based on what we are NOW (AA's) and how much this culture has influenced the world.
I think African culture is the reason AA culture has, well, used to have so much rhythm and soul. Not just musicall, but in the essence of life itself.