I made a big mistake in my post, 1000 AD not 100 AD, now corrected. I've also heard the story of the Portugese getting to N America first, and there are even stories of a vast copper mine in Canada run by the Romans, not to mention Chinese voyages in the historical record. The difference here is that they've got the map, and they've got several artifacts found in N. America. No doubt they weren't 'first,' but this is the oldest documentation yet found. themap has always been controversial, but this new study puts to rest some of the claims of forgery.
BTW, DNA studies have not confirmed the European Hypothesis. The latest and greatest study claims all Native Ameroicans case over the Bering Strait, which is an old theory. I'm not sure how extensive this study is, so I'm banking on the jury still being out on this one. I'll try to find the DNA reference...