there is actually a fair amount of evidence suggesting early contact between europeans and the northern indigenous groups like the cree in the form of r1* genes in the indigenous population. the initial explanation i was given for this was the hudson's bay company, but the prevalence is so high that it suggests something earlier. and, we've even seen theories develop that suggest a saami origin for some indigenous groups, rather than a movement over the bering strait. 

the reality is that we know there were r1* carriers in the region quite a long time ago, and a norse origin is the easiest answer.

i know the kensington stone is a fake, but the idea appears to be grounded.