The claim that the American poor are wealthier than the French middle class is rather loaded, and looking at it from a specific set of norms. I've spent considerable time living in both the U.S. and Europe, and in some ways Americans are indeed wealthier, but in some ways even America's middle-class doesn't live up to what Europeans expect of a middle-class lifestyle. That report seems to be measuring solely ownership of some material goods. But some of them are negatives from my perspective! I do not want many of those goods, and many Americans are essentially forced to buy them, whether they like it or not. That makes the American of the same income live
less well off, because they have to spend their money on them.
Example: you have to own a car in most parts of the U.S. to get anywhere (such as work), because transit sucks. You don't in most of Europe. When I moved from California to Denmark, I sold my car, dropped my insurance, and don't pay for maintenance anymore. That former money-pit is now extra disposable income for me. With the same income, I feel wealthier. In practice, this is a huge problem for my poorer American friends: car payments, insurance payments, car repairs, etc. are a huge issue for them. If something breaks they have to come up with money to repair it ASAP or they can't get to work and they might get fired. Whereas poorer Danish people don't have this headache; to get to work all they have to come up with is a bike, or money for the monthly transit pass (I pay $50/mo for mine).
Not to mention that Americans have an endless list of other expenses: they're expected to pay for their kids' college, their own health insurance, they don't get maternity/paternity leave or daycare provided, etc., etc. Even the middle-class Americans I know seem poor compared to an average Dane, in the sense that they don't feel economically secure, and are constantly stressed about money and the future. Whereas even a lower-middle-class Dane generally has smooth sailing and an economically secure lifestyle. Sure, fewer microwaves and cars, but who cares? Since this thread is about money buying happiness, it doesn't seem to have translated into Americans being happier than Danes.
But mostly what appalls me about the U.S. is that it doesn't really seem first-world if you walk into poorer areas. Stuff looks incredibly run-down, and people literally fear for their lives! Right in the middle of major cities, too. When I lived in Atlanta, I had to be very careful about which streets I walked on after sundown (and not only because of the tripping hazard, since the sidewalks were all in disrepair).