The problem is if we use OTL as an example the Norse didn't do that. The Matryoshka analogy I used plays out very accurately with Norse settlement patterns. We see Norse arrival in the British isles before an eventual group, predominately from the British Isles settles in Iceland (it should be noted that much of the Icelander population's ancestry can be trace back to Ireland). A further group from Iceland established themselves in Greenland, and for the most part any further settlers came from Iceland as well. By 1000 there was essentially no new settlers coming to Iceland from the Isles or Scandinavia - let alone going to Greenland! Vinland in turn was colonized mostly by Greenlanders, which is especially notable given that Greenland had ~2500 people at the time. Best we can tell is that the Vinland population numbered at 150 at most. Those are the population numbers we're working with, its incredibly small,
Well Leif Erikson himself was from Iceland and Greenland was just being settled at the time, your matryoshka example fails there outside a strictly geographical perspective given the settlement of Vinland happen virtually concurrently with Greenland. In any case while the insular Norse would be in a better position or more prone to migrated to Vinland, they don't need to be the only one, when a stable settlement is created we can have Norwegians join in too.
and yet still people are postulating that the Vinlanders are going to spread out over the entire Saint Lawrence Seaway and even overcome the Mississippians, its utter nonsense.
Well the English settlers didn't overrun the Sioux or many other Amerindian groups until the 19th century, but they certainly built strong and permanent settlement over large territories within the previous 2 centuries and they also started incredibly small and with a couple of failures. We are always talking about centuries there, not just a couple of generations.
I don't see why out of all the hundreds of population replacements or just major demographic changes that happened just about everywhere in the world this one is impossible, someone should'tell the Austronesians or Polynesians that they had no chance in settling Madagascar or Hawaii or contacting South Americans.
The Vinlanders are going to have a hard enough time establishing themselves where they are for quite some time. Sure, Vinland sending settlers out itself is pretty par for the course for the Norse, but once they hit the Saint Lawrence they're going to come up against settled semi-agriculturalists, and the Norse settled population isn't going to displace them, they didn't do so in places much closer to home where they *had* a potential settler population advantage. Vinland isn't going to have that. They can do it on Newfoundland where the Beothuk are a small hunter gatherer population, but that's not going to happen on the much more populous - and agrarian - Saint Lawrence.
But if they could not do that close to home, where there demographic numbers are, why on earth are they going to do so on the other side of the Atlantic?
Who should they have displaced? Also this is pure circular reasoning, we can point at actual events behind why the Norse didn't have a lasting linguistic impact in various regions and even in IOTL we see plenty of lasting effects, with the important Norse influence in English grammar(more than any Celtic substratum ever really did) or the the Cait, Orkeney and Shetland were Norse speaking into the early modern era.
Also none of the populations encountered by the Norse in Europe(outside the Sami) were comparable to the non-agricultural populations in Atlantic Canada, in density, raw population numbers or technology.
But even with a rather aggressive 1% growth rate the combined Greenland/Vinland population is numbering barely above 10,000 after 150 years! Vinland itself probably won't make up half of that number, Newfoundland is not exactly paradise after all, and Greenland has a head start.
Newfoundland is not worse than Iceland, if anything cliamte-wise most of Newfoundland is better than most of Iceland. This alone would make settlement there more favorable and really allow for thousands of people to move within a couple centuries given the right circumstances.
The Varangians couldn't even do it the scattered Slavs and Finnish tribes in the Rus lands which are right next door to Scandinavia and directly connected by well established trade routes to their homeland!
The Kievan Rus had probably many times the population of any Atlantic Canada or even Northern Scotland. It's not comparable, it's apples and oranges.
"The Spanish did not replace linguistically Neapolitan or Dutch despite them being next door in Europe, why would they assimilate the natives in the Americas?", that's the idea. Those are 2 different processes, involving populations with different cultural ties, there is no Christianity or universal organized religion in the Americas which already massively changes things.
Aside from Iron tools and domestic animals, the Finns and Slavs in Rus are not dramatically different in lifestyle to the Saint Lawrence natives at this point. It bares repeating: if the Norse settlers can't supplant a population right next to there Heartland, how are they going to do it somewhere where they are barely even established?
First of all, no they are completely different, high medieval Estonia alone had between 100k and 200k people and I believe between 50k and 100k in the viking period, that's quite dense compared to Atlantic Canada and by itself it's 10-20% of the total population of pre-Columbian Canada(according to the Canadian institutions I believe).
Also those populations have been agricultural for millennia and Estonians themselves were active groups, raiding the Norse and maybe participating in the Finnic expansion/colonization of Finland that was undergoing during this period. So their shipbuilding was good too, on top of iron working, horses, livestock and a millennium of experience with all the previous listed points.
Second, as far as we can tell the pagan Norse never really conquered the Finns or Slavs in a direct fashion like we see in England or later with the Christian kingdoms, their role in the Rus state as far as we can tell was one of middleman elite with small numbers and openness to intermarrying. This is not some universal statement on how the Vikings or people with Norse genes are going to act at any point in time in history anywhere on earth.
The estimates I know for the at-contact Iroquois-speaking populations around the Great Lakes and the St.Lawrence are about 40 thousand and 60 thousand. The St.Lawrence is certainly accessible to an established Vinland in Atlantic Canada with anywhere between 20 and 50 thousand people by 1300 if we assume about 10 and 20 thousand migrant settlers from outside over 3 centuries and an average annual growth of 0.5%(compared to the 0.2-1% growth in Iceland during this period or the 0.2% growth in Scandinavia).
Edit: The Iroquois figure can certainly be too low, using this map:
I estimate between 80k and 200k Iroquois, the higher figure is maybe too high for the overall figure for Canada of 500k, it still doesn't make a Norse infiltration impossible or unlikely given the demographic situation outlined above.