Archeology and DNA studies prove that there was far greater pinprick movement of peoples than earlier studies had ever imagined. Still, very few of these were for any length of time or purposeful, with the exception at present day knowledge of the Vikings in Greenland and L’Anse aux Meadows on the northern tip of the island of Newfoundland.
Landings by hunter-gatherers, by storm-tossed sailors and unintentional stops for water and food are by chance and end with no lasting contact or permanent results.
So no matter how the history is told, the one permanent results discovery is that of 1492!
This study seem to show that Europeans were here more than 10-12 thousand years ago and perhaps as long as 26 thousand years ago, while the DNA evidence shows no trace of Europeans them. This seems to fit the Saginaw manifold hypothesis as the reason for the megafauna extinction and the vanished European population, followed by re-population from Asia. It probably rained for more than 40 days and 40 nights in the western hemisphere, with North America being pocked with Carolina Bays. Just my SWAG.