How do you tell the difference between a Chinese and a Japanese person?

There are definite visual differences between them, but it takes lots of exposure to detect it. Not something I can explain easily.

Most Chinese people look nothing like Japanese people.

Umm....you can just kind of tell. There are some facial features the Chinese have that the Japanese don't and vice-versa.

The same way you tell a British person from an American.

by hearing them speak? lol , you can't just tell the difference between someone's nationality. how can you tell the difference between someone who's Finnish and someone from Germany? It's kind of a stupid question..

Easy! Japanese bow their heads even to their peers socially all the time, Chinese people don't.

https://www.google.com/search?q=Japanese+people+bo...

I don't know how to explain it but we/east asians just can tell it. There's a distinguishable look that can't be explained

I can't