Washington and Lincoln were two presidents deeply involved in trying to forge a unified bourgeois nation-state out of the European settlers in the United States. And the Thanksgiving story was a useful myth in their efforts at U.S. nation-building. It celebrates the "bounty of the American way of life," while covering up the brutal nature of this society.
http://www.peopleofcolororganize.com/analysis/native-blood-myth-thanksgiving/#more-998