Don’t let the 15 degree+ differences in latitudes fool you, a lot of the Nordic population lives near the sea, so low altitude and plenty of sea current temperature moderation.

January temps in Oslo aren’t much different than Boston. Absolute record low temps are similar too.

Coldest temp ever in Oslo is -30C in the 1800s.

Coldest in Boston was -28C in 1934.

Still doesn’t explain the poor adoption in USA but helps explain why they still work so far up north. The nordics can be relatively balmy to Wisconsin or upstate New York.