So trustworthy recollections of comets can be passed down for over 1,100 years by oral tradition (before any Europeans were in the area)? Can they prove that the tribes living there at the time of first European contact were already living in that area at the time of catastrophe?
Well, they’re talking about archeological data that itself includes evidence of the strike(s).
The Hopewell were not living there at the time of European contact. The Hopewell were very good astronomers, as well, building mound complexes that were laid out according to their observations of the sky. There are also petroglyphs all across the midwest depicting comets and the like.