The cock is not a American game, or at least not a pure one. I have never seen a pure American game with that type of comb, which looks walnut. They may show up in various variations of pea (triple)/straight (single) comb. And some birds even have Spanish gamefowl in them, so I would expect rose combs are able to come into play though it is very, very, uncommon.
His body is awfully bulky, and when I look at him I see "Brahma". But I do agree, he most likely has American game in him, and if you crossed him to a feather legged bird (Silkie, Brahma, D'uccle, etc) I'd bet they started throwing feathered legs (if part Brahma). (From my understanding, feather legs don't really show in first generation since often the parents both have to have the feather legged gene because "though it can be dominant" they're recessive genes. It would be expected to possibly get sparse feathering in F1 I do imagine though, but it would be nothing like they should be.)
-Daniel
