They did leave a genetic legacy up north in ancient remains like Anzick-1 and ancient Channel island remains [1]. That legacy simply no longer exists among most

They did leave a genetic legacy up north in ancient remains like Anzick-1 and ancient Channel island remains [1]. That legacy simply no longer exists among most remaining native populations in the US and Canada. Moreover, they're still clearly related to North American natives, it's just a more distant relationship. So it's not that North Americans and South/Central Americans descend from different ancestral populations, the population structure is just poorly understood. [1] doi.org/10.1126/science.aar6851