Is this really the case? Imagine you're at a masquerade ball with 25 people from random countries around the western world, 5 of whom are Americans from various states. Everyone speaks perfect, mechanical, unaccented English, and you are not permitted to discuss dead-giveaway topics like geography, political parties/candidates, specific foods, etc. How confident are you that you could pick out the Americans?
IMHO there is a common theme in the philosophy of life of most Americans. For example, many people have remarked on the high levels of optimism found in most Americans. It is one of my favourite American attributes.
> you are not permitted to discuss dead-giveaway topics
You might as well say "can you identify someone's cultural heritage without discussing anything that would allow you to identify their cultural heritage?". This stipulation makes the task definitionally a matter of chance.
I have zero confidence I would be able to pick out the Spaniard, Belgian, Canadian or American.
I'm having a hard time matching your generalization with my experience. When I started travelling I was surprised how similar people were regardless of where they were from.
Sure you can dig into political views and find themes but those aren't consistent or pervasive enough to make predictions on an individual basis.
Ah. My comment assumed its parent comment was written by an American. My point was that, if you hailed from an country with a common culture, it would be trivial not pick folks out of a crowd who share your cultural background. I don't think that Americans would not have such an easy time doing this.
The easiest way to see this, if you grew up in the U.S. and have not traveled much, is to read tourist guides for your own country.