What are the social archetypes that appear in Chaper 3 of Lies my teacher told me? How do they serve the Thanksgiving story?

One archetype was that of American exceptionalism; the belief that Americans were exceptionally good beginning with the landing of the Pilgrims at Plymouth Rock.

The other two archetypes as mention in Chapter Three;

"Like other Americans who have not studied the literature, the authors of history textbooks are still under the thrall of the “virgin land” and “primitive tribe” archetypes; their most common Indian population estimate is the discredited figure of one million, which five textbooks supply. Only two of the textbooks provide estimates of ten to twelve million, in the range supported by contemporary scholarship. Two of the textbooks hedge their bets by suggesting one to twelve million, which might reasonably prompt classroom discussion of why estimates are so vague. Three of the textbooks omit the subject altogether.”

I believe the author's intent in this Chapter is to deem the story of Thanksgiving as "America’s origin myth."