I've got to sit with Aiontay on this one.
Thing is, we've got enough archeological evidence for things like the spread of the bow and arrow from the Labrador Eskimo around 2000 BCE to down through the Americas, and we've got some evidence of corn spreading out of Central America by around 1000 CE. What we're missing is substantial evidence of technical or biological transfers from the Old World to the New, with the exception of those Chilean chickens and (possibly) Mayan bark pounders. Not great.
Even at L'Anse Aux Meadows (
link), we've got good archeological evidence of the Vinland colony, and material from it shows up in Indian archeology sites. But we don't see the Indians learning to make iron tools from the Norse. Ditto with the Norse Greenland settlement.
Similarly, the only good evidence we have for New World to Old World transmission is the sweet potato from south America making its way into Oceania, probably again from Chile. Again, not much.
It's a wonderfully seductive area to theorize in, but with the exception of the sweet potato transferring to Oceania, there was little in the way of definite technology or cultural transfer. Even with millenia of potential contacts, that's kind of a sad result.
Best,
F