And the Irish were probably here around 800 AD. As you said, Columbus made something of it the others are interesting historical footnotes.
I also recall reading somewhere that English and Irish fishermen were regularily visiting the Grand Banks off of Nova Scotia and New England prior to 1492 and were certainly aware of the land mass just beyond the fishing grounds to the west. However, they kept that secret to themselves because, well, they're fishermen...
However, what does that matter? Phonecian, Irish, Scandinavian, Chinese exploration fleets, fishermen, may have all visited portions of the Western Hemisphere. They came, they saw, they didn't do much about it.
It was only after Colombus that permanent contact was established between the Western Hemisphere and Europe (and the rest of the world later on).
BTW, Semper Fi!
Yes. I read recently that archeologists on the east coast discovered an ancient kitchen midden with the remains of a boiled potato and several empty bottles of Guinness. ;^)