We know North America was mostly filled with hunter gatherer tribes. So the population would have been low compared to even South America, but especially Europe

We know North America was mostly filled with hunter gatherer tribes. So the population would have been low compared to even South America, but especially Europe and Asia. We don't know all that much about the supposed impact, as you say. Just that more large mammals in North America went extinct than anywhere else, so it was likely the worst affected.