First of all, it compares figures from two different data sets. That is usually something that is quite hard to do correctly, because different data sets usually use different definitions for stuff like "household consumption" etc. Without a peer review it is really hard to tell if they've done it correctly and given the intricacies of economic statistics, my guess is they didn't.

But maybe even more importantly, the data concentrates on "private consumption" and thus leaves out all the goods and services that governments pay for – which is the entire point of public services like a public health care system. I.e. when a poor person in the U.S. visits a doctor, they pay for it out of pocket, the transaction will be registered as "private consumption". If I (in Germany) visit the doctor, no money ever changes hands. My contributions to the public health care system are deducted from my income before it ever reaches my account and about half don't come out of my own paycheck anyway, they are the responsibility of my employer.

So my guess would be that this "study" undercounts exactly what it professes to account for: Goods and services consumed (but not necessarily paid for) by the poor.

But how about we measure outcomes? For example in terms of life expectancy, the U.S. is much more "unequal" (if you are poorer, your are more likely to die younger) than other developed economies: https://ourworldindata.org/life-expectancy#inequality-of-lif...

And because the U.S. has worse life expectancy than other developed economies in general, poor people are likely to die younger in the U.S. than in, say, Germany in absolute terms as well. That is just one indicator but if you accept that "the number of years you live" is an important indicator for general quality of life, the U.S. seems to score quite badly on this.