I've heard that clearing the table of food would be considered rude in China, as it means you didn't get enough to eat, almost exactly opposite to the only food-related rule I was ever taught growing in the US - never waste food or serve yourself more than you can eat. That's probably just a "my family" thing though. I get the impression that even saving leftovers is rare among Americans these days.

There are still contradictory customs around this enough that it is standard practice to warn exchange students from Europe that if they finish absolutely everything on their plate that this is a signal in many American homes that you should be served more. This can lead to some real discomfort as the student tries to eat everything they are given which leads to being given more and more.

So at the same time it is considered poor taste to take more than you can eat, it is also considered poor form to offer a guest anything less than more than they can eat. This also shows up when people rate restaurants by the serving size.

Which is funny, because the serving sizes in US restaurants are so big that no human being can be expected to eat it all.