Which former Governor of Iceland claimed to have discovered America 20 years before Columbus?

Would you be referring to Didrik Pining?

That's the man. Source. Thank you Sailracer.

So he felt he beat the Vikings, who beat Columbus by about 500 years, and the Chinese, who probably beat the Vikings by about 1500 years? While he can't be expected to know about the Chinese, Ericson's trip was certainly know in Iceland at that time.

So right. How about the "Clovis culture" which is most probably the right answer about the first people in the "new" world.

look at this

Except, possibly, for the two other cultures mentioned in the Wikipedia article.