Oh boy! Quite a debate on religion here...
Here is what I think/thought:
When we started on this i had the same view as James - the Icelanders and Greenlanders were Catholics (they actually converted before most of Norway did), the Vinlanders came from there -> thus they should be Catholic.
Since then I have read a bit more about the Vinland saga, and have realised that although Leif Eriksson was a Christian many of his companions in the explorations were not. Of these the most prominent in the sagas is Thorfinn karlsefni who settled and lived several years in Vinland before returning to Iceland.
This is the historic info. If we now consider how a Vinland settlement would attract settlers I think the possibility to avoid submission to
Kvitekrist (norse name for Jesus) would be one reason to resettle in Vnland - this way you get a community mostly of ancient norse beliefs, and this would also explain partly why they have broken contact with (Christianized) Europe.
In the end this is a matter of gameplay, and creating a fun scenario. There are no historic proofs supporting either ways, but by starting as asa-believers you have the extended possibility of creating some great events e.g. for the contact with Europe, European missionaries etc...
By making the Vinlanders Catholic in 1419 there is IMO no more possible changes to religion... They would not return to asa-beliefs after 400 years as Catholics...
This is the reason I suggest the following:
- The Vinlanders start as an isolated asa-believing community (using a modified hinduism), and this is one of the reasons why they once broke with the Catholic Green-/Icelanders. They should also start in one of the slower tech-groups (china?) because of missing impulses from Europe over the past centuries.
- After contact with Europe they should receive random missionaries working on their own, as well as official attempts on conversion from catholic states. This should also improve their techgroup (and also reduce their relations with the NA indians?).