Wages started to diverge from productivity at about the same time as the USA opened up to non-Western immigrants in 1965:

https://en.wikipedia.org/wiki/Immigration_and_Nationality_Ac...

"The act greatly increased the total number of immigrants as well as the share of immigrants from Asia and Africa."

Immigrants from poor countries are easier to exploit, and will accept lower wages/standard of living, because their 'new life in the new world' is still superior to their homeland.