Less than you'd think. The white sands footprints push things back far enough that virtually all coastal sites would have been destroyed by glaciers at the LGM. We're still trying to map out the specific details.
Maybe if you specifically care about "the first people in North America". But even if that was really 20kYA+ (wild that this is a serious possibility now!) there's still a vast gulf of more recent prehistory that we know so little about. And there's probably loads of fascinating evidence to uncover.