You can call it "upper middle class" all you want, but to the vast majority of the population those folks would simply be "rich".

I'm not as concerned as you with the various strata of richness and the mobility between them.

I'm much more concerned with the social mobility of people living in poverty, which is pretty bad in the US compared to Europe. [0]

Key factor in that? Unions.

[0] https://en.m.wikipedia.org/wiki/Global_Social_Mobility_Index