It is silly. Your example isn't even about a wealth tax, it's about an inheritance tax. Sweden has a 30% Capital Gains tax (likely the vehicle for any form of future wealth tax) and seems to be doing much better than the US.
Sweden -- along with virtually all European countries other than Switzerland, Norway and Luxembourg -- have much poorer middle classes than most US states.
https://www.aei.org/carpe-diem/if-sweden-left-the-eu-and-joi...
https://mises.org/wire/if-sweden-and-germany-became-us-state...
Switzerland, Iceland, Luxmbourg, Belgium, Ireland, France, UK, Spain, Austria, Italy, Malta, Norway.
If you go by mean wealth on the other hand, only Switzerland is higher than the US. But that is not a measure of middle class wealth.
Source: https://en.wikipedia.org/wiki/List_of_countries_by_wealth_pe...
Americans with savings rates that are comparable to Europeans end up accumulating tremendous wealth over their careers, even in the middle class. This is offset by the majority that spend every penny. That Americans don’t save their prodigious income is an unfortunate artifact of having multiple generations of nearly unbroken prosperity.
Sweden typically ranks much higher on class mobility measures than the USA.
Accumulating wealth is the only way poor people can stop being poor. Of course it's related to class mobility.
A society that emphasises wealth accumulation above all else will have the privileged accumulate so much wealth it'll be nearly impossible for the poor to catch up, no matter how talented or hardworking.
One way of measuring class mobility is looking at your liklihood of finishing your life in a higher 'class' (variously definied) than you started it, or than your parents had. With that kind of measure, Sweden does extremely well. Certainly much better than countries like the USA, which arguably do emphasise making the accumulation of wealth (when you already have a lot of it) easier.