The book Mayflower by Nathaniel Philbrick clears up some of the mystery about the Pilgrim landing and why it occurred unopposed by the indigenous people of what is now Massachusetts.
Apparently, the fishing grounds of the Grand Banks and Georges Banks (not called that then, of course) had long been known to European fishermen, who voyaged out there frequently. However, there were also frequent shipwrecks, dory fishermen lost in fog and storms and other castaways, too. Some of those undoubtedly landed in present day New England to winter over and wait for rescue during the following fishing season. (Since they didn’t have families, but had left them behind while they fished, they weren’t about to colonize the place, simply survive as long as needed, and then leave.)
Undoubtedly also, this was the primary vector that eventually introduced smallpox into the New World in that place, because when the Pilgrims landed in 1620 the native populations had been recently decimated (almost literally, reduced by 75% or more) by that disease and were still suffering. They were in no condition to oppose a landing by the Pilgrims. This also helps to explain why one of the natives, Squanto, spoke English: he had learned it from fishermen and occasional coastal sailors visiting the mainland.
I would not be surprised to find that the natives rebuffed the Viking landings, if they were unaffected by disease at that time and in great numbers. After all, we’re talking about Martha’s Vineyard, Nantucket and Cape Cod. People still aren’t allowed to walk the beaches unopposed.