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Indeed there was contact around 1000 AD by Vikings, sailing in their extremely seaworthy long boats. Settlements of theirs have been found and dated at the site of L'Anse aux Meadows in Newfoundland. Other possible sites are under study.

There may have been contact along the Pacific Coast as well. One archaeologist has suggested that one of the earliest cultures to make pottery in Peru may have had contact with adrift Japanese fisherman, who were making pottery at the time.

Scandinavian and Scottish lore talks about selkies, strange creatures who may have been Inuit straying far from home in their skin kayaks.

Other contacts have been proposed. There undoubtedly was contact, but it was inconsequential for the most part until 1492. I am unaware of any evidence of the Black Plague in North America prehistorically, although it is present today in rodent populations in the western US at least. Anyone have more information?