This might be an opportune time to revive interest in
Ridwan Asher's Temperate North Pole. I suggested there just such a survival/extension, in the form of Scandinavians (mostly Norwegians, one would expect from the geography) heading north and toward peoples living on the shores of the Arctic Ocean (habitable and in some places under cultivation, ITTL). A specific possibility is an exodus of anti-Christians, founding refuge states beyond the reach of European missionary Crusaders. And thus playing a role of hostile intermediaries blocking direct access to the China trade otherwise potentially available to Europeans in the early modern period analogous to the role of the Ottomans in the Med.
The Norse could intermarry with and syncretize with peoples on all the Arctic shores, Eurasian and American, as well as from this much larger base than Greenland (which itself would also be much more hospitable ITTL), spread south along both Atlantic and eventually Pacific coasts of North America. They could also go down the Pacific coast of Asia but would run into the Japanese, Koreans, and Chinese there.
Cross-cultural wackiness ensues. Notably an early, moderated, but long sustained contact between American peoples and both the Eurasian disease pool and its technology as well as draft animals. Thus if someone like Columbus did eventually set out from Southern Europe due west (instead of to hostile Viking Greenland/Newfoundland) he'd find a much tougher challenge in subjugating his "Indios," whom the Nordics would possibly still call "Skraelings." No European conquest of the Americas then, except insofar as the syncretic penetrations of the Nordics counts as such. I daresay Christian Europe would find its ways to worm into relevance overseas; entirely possible some of the refuge Viking realms would belatedly convert to one form or another of Christianity, or at any rate engage in mutually profitable relations with some European power or other on a more secular basis, and the same might be true of stronger, more durable Native American regimes. Some might come under European sway on the Indian or Chinese model. But then again, the conquest of the Americas was a major driver and enabler of European global expansion--without that, perhaps the whole Industrial Revolution would be forestalled.
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As for a less ASB setting where the polar regions are indeed a frozen barrier as OTL, the problem for the Aesirists has been outlined already--they had their backs to the wall, and the only escape for them was the narrow passage of North America via Greenland.
IIRC, Iceland OTL converted to Christianity via a majority vote in the Thing, their sort-of Parliament. When wondering how an anti-Christian Paganism might have survived, one should not underestimate that Christianity often did spread by positive attractions as well as via the sword. It was generally necessary to secure the allegiance of a strong king to impose the new religion on a disgruntled minority by threat (or execution) of extermination to be sure! And syncretism is characteristic of modern European Christendom and is the result of lots of people continuing old practices and presumably beliefs more or less under wraps.
"Positive attractions" of Christendom included access to the larger sphere of societies that were already in its circle, as well as (possibly!) stopping them from sending more Crusaders. That's why I suppose if Aesirists were to have a chance to survive independent and on their own terms, they had to see alternative spheres to associate with--the Temperate Arctic would have offered that, and they might have been able to close the door after them. Perhaps they could even have lent strength to a northern Norwegian kingdom that might have held out, or at least converted to Catholicism on tacitly accepted ambiguous terms that blocked pursuit attempts and made North Norway a controlled and guarded gateway between the two spheres, and thus a prosperous and powerful middleman in both the American and China trade.
