Even if Europeans are twice as good at turning a dollar into a smile (and how could anyone believe such nonsense), the middle-class American still has three times as much money.
And either way, the problem to solve is creating the most overall wealth and well-being. Being better at a sub-problem (money->happiness efficiency ratio) is less important than overall effectiveness.
* Wealth includes house ownership, but in many EU countries living in a rented apartment is normal and even preferred, mostly because strong regulatory protection of tenant's rights. As an example our family could easily afford owning a house in the suburbs but still lives for rent in the city, because quality of life is better here.
* In the US, wealth includes savings for pension, whereas in many EU countries pensions are organized collectively, like an insurance. In other words most EU pension schemes are not visible in wealth statistics.
* Same for healthcare. I know of noone in my social circle saving for eventual healthcare crises because that is cared for by health insurance.
I know I'd trade a very large portion of my very large salary for assurances that that wouldn't happen. I don't have the option, though.
Guessing the way retirement works in the US is a large part of the difference in net worth and millionaire calculations.
Either way, lots of the difference is sure to be among the elderly (they’re who have any net worth of note, the actually-rich excepted) and you need a whole lot more money in your private accounts to have a comfortable retirement in the US than in the EU.
Once you account for in-kind and de-facto cash transfers, America's poor are supported at a lifestyle which is close to the median American household and significantly higher than the median European household.
Are you sure?
According to [1] (page 139), 36.4% of US adults have net worths between 100k an 1M, and 8.8% are millionaires. 26% are under 10k, 45.2% are over 100k.
But 32.8% of Europeans are under 10k, and only 29.5% are between 100k and 1M, and only 2.7% over 1M. So 32.2% are over 100k.
Median wealth for the US is 83k, and for Europe, it's 26k. (page 130).
Looks like Europeans have a far larger proportion of poor people, and far smaller upper middle + millionaire class.
[1] https://www.credit-suisse.com/media/assets/corporate/docs/ab...