According to Wikipedia Pope Nicholas V gave instructions to send a bishop to Greenland in 1448, just 44 years before Columbus (re-)discovered America. This doesn't make sense to me. Did the pope know about Greenland but the knowledge was not wide spread? If so: why? I'm assuming the norse settlement of Vinland had been forgotten by then (It hadn't existed for approximately 400 years). But if at least some people in Europe knew about Greenland, why didn't anyone get the idea to explore further from there? Its only 35km from the north of greenland to the next big island, Ellesmere Island.
As I explained a bit before in: Did other people in Europe know the Norse had contacted the indigenous people of Canada and Greenland?, virtually all of the "Greenlandic" bishops mentioned in the 15th century was primarily titular - just as "Latin Patriarchate of Jerusalem" in Later Middle Ages. We don't have evidence that any of the appointee actually took a visit in Greenland on field.
Besides, "Vinland" tradition does not necessarily presuppose that the land west to Greenland was the unknown continent, that is to say, America(s), as I also illustrated in: Why did the Scandinavians forget about the SKraeling (Inuit Peoples) after Viking Contact? Or did people in Iceland and Norway maintain contact with Greenland?
Its only 35km from the north of greenland to the next big island, Ellesmere Island.
On the other hand, it is true that some Norse-related archaeological finds have been found in Ellesmere land and in the Baffin Islands, usually identified with Helluland in Old Norse texts.
+++
As for more details, I also arranged links to the relevant posts with a brief summary of the histriographical discussion in: I've often heard the argument that Vikings had rediscovered North America centuries before Columbus stumbled into the Caribbean. Did they know they were on an uncharted continent? If not, where did they think they were?
(Edited): fixes the broken link.