I sometimes fly out of a small, local airport that only has one commercial route, from that airport to Philadelphia. That airport closes down overnight and it's perfectly reasonable. (And they open up at 5 AM to start serving passengers boarding the 7 AM flight; again, perfectly reasonable since there are 50 seats on that plane and you get through security in 5 minutes). But a major international airport that has incoming flights all night long? I agree, they should have at least ONE customs location staffed somewhere in the airport, any time an international flight is scheduled to arrive.

P.S. It's not just America. I flew through the Middle East once on my way to eastern Asia. The flight landed at something like 3:30 AM local time, and the security checkpoint didn't open until 4 AM or 5 AM or something like that. There were so many people waiting in line for that checkpoint, it was getting dangerously overcrowded in that hallway, with more and more people arriving down the escalator all the time. Thankfully nobody fainted or fell, but it could have been a bad situation there.

> I sometimes fly out of a small, local airport that only has one commercial route

That one, sure, but I'm referring to a few major hubs where 10-15 aeroplanes arrive before or within the first 15 minutes after they open