I wouldn't call it "downplaying"- there simply isn't enough evidence to bother talking about it. When hints at the possibility do pop up (e.g. Polynesian contact with South America), there are people who study them seriously, but those hints are so small and anecdotal that they don't make waves beyond the immediate field. You can find more information on the topic here

Also, Vinland isn't an example of a 'settlement' per se—we just don't have a better idea for what to call it. The sagas say Vinland was primarily visited as part of efforts to explore potential resources, and the archaeology suggests that L'Anse aux Meadows was more of a 'base camp' than a settlement. In particular, there's absolutely no evidence that the occupants brought any livestock (or possibly even women) with them. It was a company town, just like early Jamestown (or modern McMurdo Station), but it was abandoned without any effort to turn it into a more permanent and enduring community.