I'm not sure how long an unmaintained wooden structure would last in Iceland's environment.
That outside view in the first panel proves this one to have
stone walls, though. Wasn't there a Disqussion about that lately, the result being that stone churches weren't the majority in the Nordics, yet numerous enough to play a role in a hypothetical post-apocalyptic "d'ya remember?" scenario?
I think if Iceland went honestly, thoroughly pagan [...] it's likely that even Icelanders in Reykjavik don't know what a church is.
Sorry, no. They mightn't have the slightest what a
Christian church would look like, but the
concept of buildings of worship is present in
candidates for Icelandic Y90 cults as well.