It was (and still is) generally accepted that ancestors of Native Americans “entered” the Americas at the end of the last Ice Age when a (walkable) narrow corridor appeared between Siberia and Alaska.
Thus Clovis (New Mexico) was considered the oldest site because it corresponds with that narrative, the Clovis culture being dated 11,000 years ago.
Numerous sites have been discovered since that are much older than Clovis. Additionally, there is evidence that humans who resemble Australian aborigines lived in South America (whose descendants still exist in southern Chile).
Some of the ancestors of Native Americans may have been from Siberia but that’s not all. Languages of the Americas are quite diverse and totally unrelated language families exist.
The “out of Africa” narrative of human origin is full of holes. Look at Australia. The ancestors of the aborigines inhabited Australia for tens of thousands of years maintaining the cultural traditions unchanged until the English fleet arrived.