I don't quite like to be treated as if I were an alien of an alien race.
When people start saying that 'the other lot' have 'pointy heads', eyes too close together, or smell 'funny', then all this tells us is that the person making the remark is prejudiced.
Of course, different people have different appearance. Obviously, we can tell with 100% accuracy if someone is black or white. We would probably know with 90% accuracy whether someone was of Greek or Scandinavian descent.
Telling apart different Northern Europeans is pretty near impossible if you base it on physical appearance alone. For example, most Germans have Slavic ancestors, and many Poles have German ancestors. Any study of surnames will tell you this.
The idea that there is an English, Polish and German 'look' that applies to most members of each nationality is pseudo-scientific mumbo-jumbo.
Now, when it comes to fashion, make-up, and so on, we have a better chance of distinguishing between different Northern European nationalities. Of course, our fashion sense is influenced by our culture, and to some extent every country's culture is unique.
However, go to any Polish city, and you'll see lots of Poles wearing England football team related merchandise.
Personally, I'm extremely interested in the 'which nationality is he/she game'. However, I often get it wrong, and I simply disbelieve anyone who claims to 'know' what nationality anyone is simply by the way they walk or smell.