This doesnt match the reporting I've seen. (Example: https://en.m.wikipedia.org/wiki/Social_mobility )
Of course, this may be twisted statistics - what are you basing your claim on?
https://www.urban.org/sites/default/files/publication/99455/...
https://www.econlib.org/archives/2014/06/unpersuaded.html
https://www.foreignaffairs.com/reviews/review-essay/capital-...
http://www.arnoldkling.com/blog/krugman-reviews-picketty/
(for some starters, if you somehow have not seen how it is not the Bible that some people want it to be?).
Also it is hard to compare Europe's norms which country-by-country are generally featuring a lot more ethnic-cohesion and have social spending heavily subsidized by America's military (not to mention much more density for things like trains)
I say this as someone who wishes there were more dense, EU-style cities in America.
Mobility is certainly not dead in America, and the middle class is shrinking because more people are moving up and making more money overall: http://www.aei.org/publication/yes-the-us-middle-class-is-sh...
I think anyone trying to say "you don't know how shitty you have it!" is akin to saying "you vote against your own interests" which is really saying "I think I know better than you" -- which is trash.
The fact of the matter is a lot of people prefer US-style suburban living.
America certainly has its share or problems, reliable/trustable Governance being a big one (social welfare spending in the US, despite the money thrown at the problem, is just not up to the standards of northern EU although certainly preferable to what goes on in southern EU -- see cohesion argument though culture matters a lot too)
See this as an example why both the left and right suck when it comes to US healthcare: https://www.econlib.org/the-case-for-european-health-care/
In fact, I would argue much of the problem in the US arises because our politicians are simply full of bad ideas and not held accountable to them. Fortunately our institutions restrict them from running amok too much.
ex: the US subways suck because city politicians allowed construction and transit unions to run roughshod over the taxpayers for years on top of increasingly stupid regulations (lol @ US being the reliable land of laissez-faire) and that is why it costs 7x more to deploy subway in the US than most first world nations https://www.nytimes.com/2017/12/28/nyregion/new-york-subway-...
Still, I am willing to bet a chunk of cash that the US generally has the better recipe for ensuring economic dynamism and mobility. I'll take the hopeful over the complacent, given the choice.
It's upper class people from Europe debating with upper class people from the US where it's better for "middle class" people.
If you've read Picketty at all, it's pretty clear there is no middle class. And the only place in the world a true and sizeable middle class ever existed was the post WWII United States from like the 50s to (maybe as late as) the 90s.
Life sucks for lower class people everywhere. I suppose it's slightly less shitty for lower class people in Europe.
According to Picketty, the capital / income ratio had been substantially higher in Europe for the last 20 years than it is the US -- and at the time of writing Capital in the 21st century, it was still higher in Europe. That is to say, social mobility -- as depressingly low as it is in the modern US -- is (and has been) MUCH worse in Europe.
America's biggest flow truly is it's greatest strength. This is the most hopelessly optimistic group of people on the planet. Most Americans truly believe that one day they'll be successful.
You know why they believe that? Because for 40 years, this was really the only place in the world where that was plausible for an average Joe. It's still one of the few places where it's even slightly statically likely.
I think most people would trade hope for a slightly less shitty life.
I think that's why Americans don't really care that much why life for lower class people in Europe is slightly better than it is for people in the US.