It's like we think all black people look similar

Do you know that Chinese in Northern China look different from those in Southern China? Example: Northerners have squarer face, Southerners have more pronounced cheekbones.
Furthermore, both Northern and Southern Chinese look different from Vietnamese.

Certainly Japanese and Koreans have different facial profiles as compared to Northern and Southern Chinese. Then why do some of them look alike? I think this is partly down to make-up.