The 16-17ka date is the divergence between Northern and southern native american groups, both related to the later (~13ka) clovis culture. Indigenous americans

The 16-17ka date is the divergence between Northern and southern native american groups, both related to the later (~13ka) clovis culture. Indigenous americans as a whole diverged from Eurasians sometime before 20ka. That initial population eventually split into multiple lineages (Unsampled Population A, Ancient Beringians, Clovis ancestors) that entered the Americas, although it's not clear what order those events occurred in. We know that there was also later admixture between Alaskan and Eurasian populations across the bering strait and groups like the paleoinuit likely originated (partially) on the siberian side of the straight, but the vast majority of indigenous ancestry across the Americas as a whole derives to the ancestors of the clovis complex. It's not clear how preclovis people relate genetically to those clovis ancestors in the absence of genetic data for them.