re: About 90-95% of the people living in North America were killed by comet impact 13,000 years ago
That's because nobody believes you, and they don't care.
I believe a comet hit at 12,900 B.P., and I believe the primary impact site was at Lake Nipigon, but I believe the effects were muted by composition, low impact angle, and the nature of the ice sheet.
I would be surprised if the Paleoindian mortality rate was that high, but I would be willing to entertain it. I think the more obvious result was a megaflooding event that changed climate, and then subsequent over predation by survivors.