The middle classes in Europe definitely don’t have more. Salaries are 30-40% higher in America (even accounting for healthcare and pensions) and the cost of living is quite a lot higher.
For instance, my salary in a small Swedish city is 45,000Kr/mo. Of which I pay 6,000Kr in rent and about 3,000 for all my other bills combined (including gigabit internet). However there’s an unseen amount that my employer pays; my 45k salary is more like 90k in company costs.
Since the city is small, I would think of this as comparative to somewhere like boulder, CO. So you begin to get an idea of what purchasing power really is here and what things are paid for automatically (like insurances).
There’s also a large differentiation in regards to social norms (25 days vacation by law, income support in the event of unexpected job loss, generous maternity/paternity leave) muddying it even more.
EDIT: This spurred me to do some research and I came across this analysis by Pew research: https://www.pewresearch.org/fact-tank/2017/06/05/through-an-... TL;DR: no matter how you measure, the standard of living is better in the US than in Europe.