> America definitely has this puritan streak of trying to be the best person you can be - or the purest you can be. Work harder, drink less, exercise more, etc.

That might describe some parts of America, but it's definitely not universal. The German immigrants that formed the generation before me were drinking more and exercising less. They were also farmers, so they didn't need to exercise.

I would argue that it's the heavy influence of immigrants from all over the world that caused the self-help obsession. Those who came here weren't a random sample from their home countries. Immigration was itself a form of self-help.