In the popular stereotype since the 2016 election, America is divided into two unappealing halves: irate, disenfranchised, often poor rural dwellers versus smug, satisfied and woefully obtuse urban elites—the latter joined in 2018 by suburbanites. The voting map illustrates this narrative: skinny coastal arms of blue, likely holding oat-milk lattes, alongside a giant, angry sea of red.

This story of division may be unsettling, but it isn’t true. Using the American Community Survey’s five-year data estimates, I studied socioeconomic...