"Nuclear Family" TLDR Early USA zoning policies deliberately encouraged segregation and car dependency and promoted a family household consisting of a Mother, Father and 2.1 children, following industrial era ideas, which are relatively new and rather stupid. Pushed to the logical limit, this led to people getting pushed into housing that is deliberately far apart resulting in increased loneliness (gender free fuckery), and weaker communities, hence "atomization".

Is it fixable? Yeah. This was covered in Environmental Sciences 15+ years ago and most cities are realizing that pedestrianized areas are wayyyy more profitable than asphalt. People complain, but the world keeps going.