A bigger problem is the oldest stuff is in South America, like at Monte Verde.
The reason the older stuff seems to be found further south is probably because of the meteor(s) disaster in upper North America around 13,000 years ago.
Sunken Civ can post reference to a book about this still largely unrecognized answer to such questions as, why were so many of the large fauna gone so quickly around that time. Also why did Clovis end so quikly, etc.