That is not known for certain.
Have you ever heard of the Solutrean hypothesis?
One of the biggest arguments against it is that the timeline doesn’t make sense. If we just pushed back the human presence on the continent to >21K then the timeline might make sense.
Everything keeps getting older.
Yes, I have heard of the Solutrean hypothesis. When I first heard of it, I really liked it, as it raised the possibility that Europeans were the first people in the Americas, the true “first nation” - which would have important political implications. But the evidence seemed to be against that - as you indicated.
However, with another poster’s mention of Mousterian stone tools (#30), that does become a possibility.