In order to tie Kennewick to Joman/Ainu kinship, a time line needs to fit. Can you suggest one?
I remember right after Kennewick Man was discovered I saw a DNA breakdown of his DNA, at the top was Ainu, then Polynesian and so on...then it completely disappeared and the next thing I saw was that the DNA results were inconclusive...by that time, the government and the Indians had managed to suppress all information. The scientiests are presently studying Kennewick Man's skeleton and I expect any/the report to be crtptic at best.
Anyway, Stephen Oppenheimer, in his book, Eden In The East, states that the oldest (undisputed) Mongoloid skeleton ever found is only 10,000 years old. The oldest skeletons found in the Americas ( minus Luzia, who looks African, Brazil) are non-Mongoloid and seem to have the same skull/body type as Kennewick Man. Now, if you'll look at the map made by Oppenheimer I've linked below, he shows and entry into the Americas into Meadowcroft 25,000 years ago that becomes isolated for a period. He mentions in the same section that the Indians in that region (Objiwa) today have a high (25%) of the 'X' (halotype) gene shared by American Indians and some Europeans only.(The link was broken by the Toba explosion 75,000 years ago.) I'm guessing that the folks who entered 25,000 years ago are related to Kennewick Man and are the source of the 'X' gene in the Americas. A good DNA study of Kennewick Man could be revealing.
It is my opinion that the Jomon (and possibly Ainu) types dominated large areas of Asia in ancient times and produced today's Caucasians and Mongoloids
I don't know why someone hasn't gone to Japan and done a DNA analysis of the surviving Ainu remnants there.