It is similar for a lot of Asian populations as well. I think it is mostly just due to how much exposure you have had to the various populations where you can notice the small differences that tend to make a group distinct. Most Americans do not interact with enough European sub-groups to distinguish between them, while most Europeans I have run into tend to lump east Asians into a single group while I can easily distinguish between London tourists who are Chinese, Korean, and Japanese just from having spent a couple of decades on the west coast of the US. When you are surrounded by different groups you tend to pick up on the subtle clues.