Sweden has a population 1/4 of California... and 1/40th the size of USA. Scandinavia is generally culturally homogenous and quite wealthy. American problems are more complex than meets the eye. It’s easy to be happy with a welfare state when most of your citizens are motivated and educated, and you have a large pool of wealth.

America still has more money per capita that most of Scandinavia (perhaps not Norway). "Culturally homogeneous" is just a dog-whistle for "nordic white". Plenty of "cultural homogeneous" places are very bad, and many "culturally diverse" places are quite good.

At the end nothing of that has to do about the possibility of having a welfare state. The decision is just political.

Compare south Europe too. Scandinavians have replaced the family/kin based support system with extensive welfare safety net. The south is trying hard to do the same and ends up with corruption. Because people don’t see the same incentives