Rav Hershel Shachter in Nefesh HaRav (p. 231 in the 3rd edition) quotes the Rav as saying, “we may eat turkey on Thanksgiving.” We can infer from this statement that we may celebrate Thanksgiving and it does not violate the prohibition of Chukot HaAkum, following non-Jewish practices. However, this approach is not shared by all Poskim. Rav Yosef Eliyahu Henkin z”l felt that we should not celebrate Thanksgiving as its origins stem from the Puritans, thus making it a problem of following Chukot HaAkum. Rav Moshe Feinstein z”l had a different approach. He writes that we can celebrate Thanksgiving and it is no problem of Chukot HaAkum, but we should not celebrate it every year for fear that our families will accept it upon themselves as an additional holiday.
Additionally, from the Rav’s statement we can infer that a turkey is Kosher fowl. Our tradition is that there are twenty-four Kosher species of fowl, and some feel that turkey is not one of them. Yet, from the Rav’s statement it is clear that this is not the case and turkey is classified as a Kosher bird.
Although the Rav gave Shiur on Thanksgiving, he moved up the time to allow his Talmidim to be home in time to eat dinner with their families.