it's an insomnia thing. you wake up at 2 am and Now You're Hungry and your damn belly won't let you go to sleep without a damn sip of milk or something silly like that.

It's not an American thing but I would argue it is how you were raised to view food things.

Many people have learned that food is a reward, that food is something you eat to smother you emotions, something you do when you're bored, something you do to feel anything at all.

Something to quell that never-ending hunger in your belly. raises hand . Turns out my family just has a history of undiagnosed acid reflux.

I've been to known to do this. When I was on a stimulant for ADHD, I would get ravenously hungry whenever it wore off, which was often late in the evening.

That doesn't really explain why it's such a trope, but my theory is that you're right about it being a US thing. It is common for us to eat dinner/supper early (like 5-7 pm) relative to some parts of Europe, which means that there's more time until breakfast and therefore we're more likely to get hungry late in the evening.