No matter the tree or its size, one can immediately tell whether someone is an American or an European in a photo still after all these years!
Occasionally I agree with orthonorm and this is one of those times. I can't explain exactly how, but there is a difference - maybe it's the style of clothing, maybe posture, maybe less of a mixture of ethnicities* - just one of those things that you know but find hard to explain. Is it always accurate? Certainly not, but often enough.
*I know that American, Canadian, etc. can be named as particular ethnicities as well but they have formed as a result of the mixing of (mostly) European ethnic backgrounds. Compare the stereotypical Norwegian, Russian, and Spaniard and you'll see what I'm talking about.