Now you might think of Iceland and Norse Greenland as a counter example. But Norse Greenland never really thrived, and was eventually abandoned. Iceland however thrived, but it is so much closer to Norway about 7 days at see with the potential to stop at the Faeroe Islands.

The voyage between Greenland and Iceland is similar (only a bit longer + sailing up the west coast of Greenland). And finally you need another week or two to cross the Labrador sea from Greenland. However that route is much harder in the winter then between Iceland and Norway, and Greenland is not nearly as populated as Iceland or Norway and don’t generate enough surplus food which they can supply to a potential colonies on the North American mainland.

So the logistics of supplying a colony in North America without help from the people already living there must include a summertime only supply line from Iceland with enough supplies to last the whole year. Where each voyage from Iceland is going take maybe a month, maybe more, just one way. These ships are still pretty small and not a lot of room for cargo, so you’ll need a few of them. I’m not sure the economy on Iceland could have afforded such an expensive endeavor.