it is not something that is inherent in poverty, either.
No that is the exact opposite conclusion actually. It has EVERYTHING to do with REAL poverty.
The problem with comparing the US to other advanced countries is that with the social services and money that is spent on them in those countries, even when you are born into a poor family in Sweden lets say, you are immediately and profoundly more wealthy than your American counterpart. This wealth isn't judged in dollars, cents and purchasing power however in excellent public transportation, strong workers rights, disability programs, top notch education for all, excellent first world healthcare, retirement benefits and more.
Societal wealth makes all the difference here. A better comparison to America would be a country like Saudi Arabia. You have a handful of disgustingly wealthy people who control almost all of the actionable power and wealth in society, a single digit percentage of REAL middle class (and I mean the real definition of middle class not this bogus American definition that was created for political expediency). If you are REALLY middle class then you are afforded modern conveniences and a level of financial, retirement, educational and healthcare security to where you don't have to frequently worry too hard about being poor in the near or long term future.
Also just like Saudi Arabia, the rest of the society is so broke they're broken, so poor they can't even pay attention.