Someone else already replied well, but I wanted to add that we’re not entirely homogenous, either. Southern US culture still has multigenerational homes as a normal thing. It isn’t the majority, but nobody really bats an eye in the South or Appalachia if you live in a home (or on piece of property with multiple dwellings) with your parents, grandparents, some cousins, an aunt or two, and that dude you brought over to dinner once that moved in at 14 when your parents found out his parents were shitty to him.