I am thinking of Tunguska here, naturally, which did a lot of damage
without leaving a crater in the ground.

I would think an airburst event might be the kind that would do the type
of destruction and death that is being claimed here.

If 90 to 95% of all Native Americans were killed in North America 12,000
or so years ago, have archaeologists found large amounts of unburied
remains? I can't believe the surviving population would be able to clean
up and bury all those who were killed and we should have evidence of
such a massive "attack" from such a geologically short time ago.

Would the Native American population have recovered sufficiently in
12,000 years to have the millions of natives who "greeted" Columbus
by 1492? Were Latin and South America unaffected and are there
estimates of how many people were living in those regions 12,000
years ago?

This is an extraordinary claim and I am just surprised that more evidence
for it had not been found or announced more widely by now.