Striking it alone by moving away from home has been a part of the American mythos since colonial times, when a big part of the Revolutionary War was the prohibition on settling west of Britain's declared Proclamation Line. And in future centuries America also soaked up all of the people in Europe who could be tempted by having a farm to themselves; they came to America daily by the thousands.

That being said, multigenerational households were really common up until the postwar period, at which point the US really started pushing the standalone suburban nuclear family as a way to avoid another case of excess industrial capacity. It takes a lot of workers and goods to build all the highways, infrastructure, and houses to support a two-story house with a white picket fence and a car in the driveway.