It is a fascinating and tragic new chapter of human history that the brilliant Clovis people may have been wiped out by a single natural disaster. But not before they left their great toolmaking breakthrough to human intellectual history. Isn't it the clovis point which marks the first and most profound threshold between ape and human? I also find it interesting that these meteor "visitations" always seem to happen at the right moment in history to shut down something which threatens to send life down too "non-diverse" and tangential a path, and spur a new general burst of growth. Perhaps Clovis was so revolutionary an awakening, that it had unbearable social repercussions for these barely human peoples, though any evidence of this is probably unrecoverable. I believe there is strong archeological evidence that the clovis discovery had spread to other parts of the world by the time the originators were (theoretically) decimated.

As far as your point about the size of the asteroid, I can point out that it is explainable that there was no crater. The suspected impact area is basically on the Canadian Sheild, which is essentially a gigantic metal plate. It is conceivable that a massive object would not create a crater there, as it would on any part of the world. There would still have to be evidence there though. Looking in the Midwest of the US won't give us all the answers.

Not all strange disappearences and changes are attributable to coment/asteroids.

When we planted trees down south, we would find different types of arrowheads in areas where that particular stone was not native to the area. Lots of tree planting inspectors were very good amateur archeologists and would offer their insights.

It made working with the Earth very intruiging.

1. How big was the comet / asteroid? It ought to be bigger than Tunguska to pick-up debris from Canada and throw it over Ohio. It ought to be smaller than chicxulub not to leave a crater.

2. Why would the explosion pick-up only precious metals and diamond and no other geologic material? If seriously scanned such evidence may also be found.

3. Is there a calculation of explosive energy needed to do the above? It has to be just right level of energy to do this. Too much would leave a big crater, too small will not pick-up debris and deposit over 2000 miles away.

4. If it is as recent as 12,900 years, there would be significant tell-tale signs over Canada, has it been found? If not crater significant charring should be seen.

5. Does the dead Mammoth bodies discovered in the recent past show such signs?

6. Is there any evidence in arctic or antarctic ice? It is too recent to be missed.

If one can answer above, the theory would be more credible.