Their parent's generation toiled really hard and lifted the entire country out of poverty and everyone was pretty well rewarded for it.

They feel working hard brings benefits.

In America, working hard brings your manager benefits. We are multiple generations into this. Most people have learned to not work hard because it is just free benefit to your employer.

Sure, we could pressure Americans to work harder by making the entire country even more afraid of losing their jobs and terrified of not overworking themselves, but even then, all that hard work will just be captured by a spoiled managerial class playing bonus games and extracting all that wealth for themselves, not for American advancement.

Even in the shithole that is American managerial culture, you can still find young Americans working hard, often in spite of themselves, because they get into some project. In the past, projects were small and your team had substantial agency, so this sort of "The team really gets into the project" outcomes paid huge dividends, and resulted in a lot of success. Things like the IBM PC, lots of stuff at Bell Labs.