American History

"they didn't come (to this site) through the interior of the continent, which would have been under miles of ice."

True, they could not have moved from north to south through what is now Canada due to the ice. But if their ancestors followed a water route along the Pacific coast and then followed rivers and streams inland across the continent south of the glaciers, they would have found many places to make villages and hunting camps on the southern edges of the glaciers. Meadowcroft is probably just one of many such sites. I would expect to find evidence of some more settled sites not too far away from the temporary hunting camp site at Meadowcroft.

The edges of glaciers have cool moderate climates that are rich with water sources from glacial meltwaters. The waters, as pools, streams, and swamps, attract game animals for the water and for grazing on plant growth around the waters.

I would bet that more sites could be found in North America by searching, west to east, along areas that used to be on the southern edge of the glaciers.