Here's one study, reviewed jointly by Dr. Henrique Schneider, professor of economics at Nordakademie University in Germany and the chief economist of the Swiss Federation of Small and Medium-Sized Enterprises: https://fee.org/articles/the-poorest-20-of-americans-are-ric...
In the US, we have welfare programs that target the poor (yes, some slip through the cracks unfortunately). Once you account for all taxes, transfers, and non-welfare benefits, the poorest 20% are on average richer than most European nations. This is measured by looking at annual per capita consumption among the bottom 20%.
The article you provided are from the same people who deny global warming(The Heartland Institute). Dr. Henrique Schneider is a conservative Austrian (as in the school) economist with loony ideas about science:
https://ecaef.org/the-anthropocene-fallacy-learning-from-wro...
So allow me to be quite skeptic about the quality and validity of his "research"
https://en.wikipedia.org/wiki/Disposable_household_and_per_c...
These numbers are after taxes and transfers, so they encode all of the welfare programs in the respective countries.