I am not sure that the Forsons in the U.S. are related to those in Ghana. My family are originally from Ghana, however, they live in Nigeria now. I think they are from Cape Coast and some of them speak Fanti. I currently live in the U.S. and have done a little research. The Forsons in Ghana got the name "Forson" from a slave master, who I believe was British. Some of the Forsons in the U.S. are descendants of the Forson clan in Britain as well.
However, the Forsons in Ghana are merely related in the sense that the British Forson, I guess, used to own, the ghanian Forson, who later bore his masters name. But thats as far as I know.