There's nothing too improbable about people sailing from Britain to North America the same way the Vikings are recorded as having done so. Rest stops at Iceland and Greenland, and then go down the Canadian coast, maybe sail up the St Lawrence.
From the Prehistoric West Virginia Site.
I remember Leif Erickson, and Mr. pre-Columbian monk... you're no Leif Erikson!
Bumping for undiscovered countries...