> is there an actual expectation of being able to tell the actual ethnicity/countries apart?

Facial structure, there are some obvious ones in ALS. But generally speaking, it's fashion that gives it away. I can spot a (relatively recent) Japanese immigrant from a hundred feet away by her clothes. It's a bit like if you see someone in Europe with a baseball cap, you can be almost certain they're American. Sandals with socks? German. Etc.