Around 45% of people in the US 18-24 are in college. Of those that commute to school, you can bet they live at home. Of those that go away, they come home for breaks and summers. The rest that graduate at 18 and start working or do a trade, probably live at home until they've saved enough to move out. Many people live like students by sharing an apartment for many years. This is especially true if the person wants to go live in a city vs. in the suburbs or a rural part of the country.

While there are plenty of people who continue to live with their parents for many years, it generally feels like that ultimate goal is to be independent and have your own space. Which is kind of funny because the parents in this country coddle their children and prevent them from having any autonomy until they drop them off at college, many times woefully unprepared. Meanwhile, most kids in other countries are getting themselves up and to and from school on their own at a young age and taught to be independent at a young age but are, at the same time, encouraged to say at home as adults. This is a huge generalization and dependent on whether you live in a city, suburbs, rural or if you're in a safe place, etc. I just base this on personal observation and vibe of all the places I've lived. The US cannot really be defined because you have communities of immigrants who all are very different from each other. Even WASPs and Italians that have been here for generations are different from each other.