A large part of the income distribution differences result from wages being very compressed around the median for a given occupation in Europe. For most occupations in the US, the top 5% earn much more money than the median person in their occupation (or the population generally), even for occupations like waiters and cleaners that we don't think of as high-paying. This creates a different set of expectations culturally; everyone knows at least a few enterprising people that make a surprising amount of money doing nominally low-wage, low-status work and therefore having access to a visibly comfortable life.
I think "poor" is relative to cultural expectations, so I am not sure how to measure that over different geographic regions. The infamously poverty-stricken regions of the US, like Appalachia or Mississippi, really do have serious systemic poverty but even the middle-class there is often viewed as poor by the standards of other regions. However, the lifestyle afforded by the 40th percentile household income in most European countries would identify as "poor" in much of the US, despite being definitionally middle-class. In much of the US, "poverty" is primarily associated with social problems like drugs and crime, not economic resource issues per se outside of a few sparsely populated regions, which isn't that different than what I see in Europe. I grew up in abject poverty of non-social kind, which is pretty rare in the US. In hindsight, I think the government did a reasonable job of handling that case.
I think "poor" is relative to cultural expectations, so I am not sure how to measure that over different geographic regions. The infamously poverty-stricken regions of the US, like Appalachia or Mississippi, really do have serious systemic poverty but even the middle-class there is often viewed as poor by the standards of other regions. However, the lifestyle afforded by the 40th percentile household income in most European countries would identify as "poor" in much of the US, despite being definitionally middle-class. In much of the US, "poverty" is primarily associated with social problems like drugs and crime, not economic resource issues per se outside of a few sparsely populated regions, which isn't that different than what I see in Europe. I grew up in abject poverty of non-social kind, which is pretty rare in the US. In hindsight, I think the government did a reasonable job of handling that case.