Yet, Ket in central Asia and Navajo in south-central North America are very closely related. Sadly, Ket is close to dead, with only dozens of mostly elderly still fluent. Some suspect it was carried in a migration from Alaska back to Asia.
Languages used in British Columbia and Yukon are in the same family to those, but less similar. It is an example of a common phenomenon, where the extrema of a range retain older features. We see it also in far-west Celt and far-east Tocharian languages. It probably explains how rare genetic features are found in common in isolated South American, Australian, and Indian Ocean refugia, and nowhere between, and in pre-contact eastern US and western Europe haplogroups. Traces between get washed out by later influx.
May be related, not “are very closely related.” There are some cognates between the two families. But no two languages that were separated for 10,000 years are very closely related.
Why do people get so attached to pet linguistic theories of all things that they feel the need to make up informants, forage sources, and generally lie in order to “prove” a claim that has literally no value if it’s not true? It’s totally plausible that the languages are related, and that’s awesome! But the evidence for them being mutually intelligible just isn’t there.
Well, it's remarkable if these languages are related, but even so, we're talking about two languages that diverged thousands of years ago, maybe 10k years. Probably in the same ballpark as Proto-Indo-European or even older.
That is, these two languages would be about as mutually intelligible as, say, English and Albanian, or less.
I have doubts as well. "Almost" may be carrying a heavy load there. People are just really good at communicating, face to face, over difficult barriers, particularly when they share cultural underpinnings. But I don't speak any language in the family, and can only go on what they say.
We actually do have material evidence connecting pre-age of discovery Siberia with Alaska via Aleutian trade and shared genetics, though, and the strength of the product of evidence is always stronger than a single hypothesis of connection in isolation. To my knowledge no such archeological or genetic link has been established between pre-Vinland saga Greenland and Iceland, let alone Norway.
(Hell, I'm not sure there's any genetic evidence of admixture between the expeditions of Erik the Red and Greenlanders despite clear cultural and material evidence of contact, though that's probably more of a testament to lack of continual trade than evidence it didn't occur at all.)
Languages used in British Columbia and Yukon are in the same family to those, but less similar. It is an example of a common phenomenon, where the extrema of a range retain older features. We see it also in far-west Celt and far-east Tocharian languages. It probably explains how rare genetic features are found in common in isolated South American, Australian, and Indian Ocean refugia, and nowhere between, and in pre-contact eastern US and western Europe haplogroups. Traces between get washed out by later influx.