The standard of living the US achieved circa 1968 / 1974, is unlikely to ever be matched again anywhere on earth by a large nation. The minimum wage at the time was equivalent to roughly $35-40,000 per year today.
A big part of the reason for that, was every US competitor got destroyed in WW2. The US inherited an open runway, and acquired over 50% of all global manufacturing at the peak accordingly.
As major countries, like Britain / France / Germany / Japan got their feet back under them, that competition drained the easy income and wealth off the top of the labor force in America. The rise of China, Brazil, India, etc and the opening up of the Soviet bloc has further stressed the US labor market, by increasing competition.
The peak that you're referring to that America has been coming down off of, was temporary and would not normally have existed had it not been for WW2. It was a fluke.
That massive concentration of income and wealth the US acquired due to WW2, has been gradually redistributed due to competition. People in Estonia, Norway, Finland, Denmark, Sweden, Norway, Czech, Slovakia, Brazil, China, Australia, Canada, etc. etc. have seen massive increases in their standards of living the last 40 years.