I still haven't heard specifically why the geographic and demographic differences we have with a place like Norway would prevent or obstruct us from having a social system akin to theirs.
Well for one, no one is immigrating to Norway like they are France/UK/Germany/Italy...or even the US and Canada.
Additionally, when your population is like 80-90% of a single background, its easier for policy to get pushed through since you all share a common history and background.
You're talking about places that ARE nation-states. As in, there were KINGDOMS of Norway...and they later became "countries"...but Norwegians are like people FROM Norway and have been there for hundreds of years. Only recently has it been possible to be from Norway and not be an ethnic norwegian...as is the case for most of Europe. The US has always been a land of diversity.
That being said...when you share a common background, people don't consider the "others" as much, cause there isn't that much that separates them socially. They're all the same people and so anything thats being considered, generally will be seen as helping each other.
Its easier for them to do shyt that seems progressive cause they have fewer people to convince AND fewer concerns to consider.