Poverty’s affect different in the US vs other developed nations

Poverty stunts IQ in the US but not in other developed countries

In a new meta-analysis of 14 psychology studies from the past few decades, researchers found that the strength of poverty’s pull differed by country, with US poverty providing the only forceful yank among developed nations. The authors, who published the results in Psychological Science, speculate that the wider inequalities in education and medical access in the US may explain poverty’s extra power. The finding could not only resolve the data discrepancies of the past, but it may also lead researchers to a more nuanced understanding of poverty’s effects on IQ and how to thwart them.

I wonder if the size of the US also has something to do with it, where poverty would affect areas differently.