I've often theorized that what we call "American exceptionalism" (and similarly Canadian, Australian, and New Zealandese) is made up of the fact these countries are very heavily populated with early-generation, by-choice immigrants.

The population was effectively self-selected for those ambitious enough to emigrate, and in many areas, tame a new frontier and/or start businesses. They were then dumped in an environment highly supportive to it (cheap land and natural resources, rapid technical advancement providing huge vistas of economic opportunity) That probably has a significant ripple effect for a few generations. (The "Grandpa had to swim across the Atlantic and learn English and sweep floors to get started, so he's going to ride his kids to make sure they get the most of their education" pattern)

On the other hand, I suspect there's some toxic counterfactors in that; the celebration of bootstrap-pullers tends to encourage "I've got mine" attitudes and may end up underserving parts of the community that would benefit from more social support and community services.