Most of these aren't really "traditional", they're constructs of the post-WW2 era, where the government & mass media/advertising very consciously tried to institute strong "national unity" norms.

I suspect that the "traditional American" culture GP is talking about is frontier/immigrant culture from c. 1840-1929. There's a good case for that really being a "shameless" culture - you do your thing, I do mine, we'll grab up all the land and all the gold and all the prime industries and not feel bad at all for the natives we're genociding.