How confident can we be that only a single breed other than the Dom American Game and breed x were involved? Also, a couple other breeds may have been around that could have had more influence than Dom American Games. Multiple parts of Europe had dom colored landraces (i.e. Scots Gray) that could have been involved. The Scott's Gray was valued for eggs and meat, existed at the correct time (pre-dating American Dominique) and occurred in a region providing immigrants to the eastern seaboard at the correct time.What is in Red I agree with and is what I have been saying for some time now.
As far as American Dominique and Dominique American Game being once interchangeable I don't think they were, now they could have been very closely related at one time.
Example being that the American Dominique could have been the off spring between the Dom American Game and a breed x.
Chris