They aren't that richer either -- if anything the majority is less rich in standard of living than most western European and nordic countries. Getting some more money in your salary is not worth much if you have to give most of it to medical coverage and basic services.
It's borderline useless for determining the wellbeing of the average worker.
Blatantly false (see the other comment re: GDP). With a few exceptions[0], the US is very close to the top in terms of overall standard of living.
[0] https://en.wikipedia.org/wiki/List_of_countries_by_GDP_(nomi...
Even regarding GDP per capita, most the "few exceptions" you mention that trump the US are western European and nordic countries with the exception of #4 Qatar.
1 Luxembourg 102,717
2 Switzerland 80,603
3 Norway 74,598
5 Ireland 61,206
6 United States 56,084 <---
7 Singapore 52,888
8 Denmark 52,139
9 Australia 51,181
10 Iceland 50,277
11 Sweden 50,050