SZ: not sure where your point about “upper class”
My point is that one of the reasons Us “middle class” is less is because the “upper class” is larger. That is not a bad thing, except for commies.
As to “culture”, OUSD numbers show that US had a (decreasing) lead on educated population over Europe from 1920s. What you define as “culture” was remarked upon by Tocqueville: Americans tend towards practical skills that are useful when going to frontier (whether physical or virtual) rather than poetry and philosophy popular among European aristocrats. So, you may be unfair discounting applied intellectuals as just “materialism”. They are the ones who connect the world though railroads, radio, electricity, special forces, internet.