Most of those not working say they don’t want to work; there are two vacancies for every unemployed person; all countries have structural change but the US stands out. Demand side economics won’t fix this problem.
My reading of the data is that increased transfer payments cannot explain the big rise in non work. There are today too few beneficiaries receiving too little for this to be the largest part of the story.
There is some social phenomenon which I suspect explains non work, non marriage, deaths of despair, general alienation and, I suspect, the rise of reactionary populism. It should be a major task of social science to understand it.