Why do international flights board incredibly faster than domestic ones?

It always amazes me the quick and efficient nature of boarding a jumbo jet with 100s of people that don’t speak English (going to Seoul) and the entire boarding process was no joke 10 mins. Everyone sat in their seats, got out of the aisle and put stuff away in a manner that seemed otherworldly. Meanwhile trying to board a domestic flight to FLL or Cali is always ALWAYS a hassle, add in the screaming child and person refusing to cover their mouth when they sneeze or cough and its par for the course. When I was in Tokyo in December same thing going and coming. No screaming children, quick amazing service, easy boarding. In the US, shambles almost every time. What do we think this is about? Are people just trying to get the f out of the western hemisphere as quickly as possible?