US immigration process while in international transit is a pet peeve of mine. Not many countries require this. Even same aircraft services are not exempt, not even if passengers are kept in a secure airside holding cell (like Air New Zealand’s London Heathrow to Auckland service). Crazy, and the main reason Air New Zealand last year started flying London Heathrow to Auckland via Hong Kong.

As for clearing immigration on domestic flights, that isn’t as unusual as you may think. Many airlines operate a domestic leg at the start or end of an international flight, which leaves from international terminal and requires immigration processing. Fortunately in most places they are set up to handle domestic only passengers (eg in Australia they have “D” stickers and separate lines at immigration), and so the main effect on the passenger is an earlier check in requirement. Some people even go out of their way to fly these flights for the improved seating, food, service.