What killed off the Clovis people

Tiny diamonds found in the soil are "strong evidence" a comet exploded on or above North America nearly 13,000 years ago, leading to the extinction of dozens of mammal species, according to a study.

The scientific report also suggests the cataclysm also reduced the population of the earliest people to inhabit the region and triggered a 1,300-year-long cold spell that stretched around the world.

The prehistoric humans known to have inhabited the continent at the time of the event -- hunters and gatherers dubbed the Clovis culture -- suffered a major decline in population in the aftermath, the scientists said.

The scientists studied layers of sediment dated to 12,900 years ago at six North American locations, including one directly on top of a Clovis site in Murray Springs, Arizona.

CNN

Interesting:

The controversial Solutrean hypothesis proposed in 1999 by Smithsonian archaeologist Dennis Stanford and colleague Bruce Bradley (Stanford and Bradley 2002), suggests that the Clovis people could have inherited technology from the Solutrean people who lived in southern Europe 21,000-15,000 years ago, and who created the first Stone Age artwork in present-day southern France.[16] The link is suggested by the similarity in technology between the projectile points of the Solutreans and those of the Clovis people. Such a theory would require that the Solutreans crossed via the edge of the pack ice in the North Atlantic Ocean that then extended to the Atlantic coast of France. They could have done this using survival skills similar to those of the modern Inuit people. Supporters of this hypothesis suggest that stone tools found at Cactus Hill (an early American site in Virginia), that are knapped in a style between Clovis and Solutrean. Other scholars such as Emerson F. Greenman and Remy Cottevieille-Giraudet have also suggested a Northern Atlantic point of entry, citing toolmaking similarities between Clovis and Solutrean-era artifacts.

Mitochondrial DNA analysis (see Map in Single-origin hypothesis) has found that some members of some native North American tribes have a maternal ancestry (called haplogroup X) (Schurr 2000) linked to the maternal ancestors of some present day individuals in western Asia and Europe, albeit distantly.
Pedopedia

So we have a European-influenced culture in North America.

It makes sense, given that if Siberians were mobile via boat or land, so were Europeans. We know they existed in China 2700 years ago, which means the routes there were probably explored long before.

And if you are a wandering group of hunters, how hard is it to range a few thousand miles? Even covering a mile or two a day, you go far.

Probably there were two groups of adventurers, European and Siberian, who came over first.

They were wiped out and replaced, as the pattern goes, with those who followed the path already forged.

These were the people who by the time the Europeans arrived, had degenerated into a third-world state of disorganization and corruption. The Aztecs should have been able to crush Hernan Cortes, but got caught up in internal politics and sacrificed. The North American Indians were so busy fighting each other they actually welcome the Europeans as allies. Clearly some mental degeneration had gone on.