Social Democracy works (in moderation) in tiny, homogenous nation-states like Norway and Denmark. The idea that you could suddenly introduce it in the USA is preposterous and imbecile. It would take decades to implement and carry a heavy burden. You cannot swerve the world's greatest nation like you do a sports car.
During their absence from real politics, the Democrats in the US have radicalized verbally. After they got back both houses of the legislative branch, things mostly go on the way they did during the Republican years. I sincerely expect and hope that the same will happen if they get the executive branch. America will have to modernize, there is no way around it, but it will have to do so in its own way and at its own speed, for the good of its own citizens and the world.