>>15444991They don't anymore.
It's a total lie.
Most white people live with their parents until 30 and beyond.
Traditionally, the answer to OP's question would be that America (and other New World countries), had a very strong, "Work hard and stand on your own two feet" ethos.
Life wasn't merely about subsisting with your family and dying at the same place you were born.
Life in the New World was about growing, expanding, excelling, enriching, improving, and so on.
Now, all that's totally gone, though.
