First, there's no indication in the picture that it was taken in the USA.

Not off to a great start here, it's not hard to tell this is USA. Between the diversity of subjects, their style of dress, the style of train, and background advertising there are a ton of clues. Plus why would I lie?

Second, the person I'm replying to doesn't indicate that he means the USA, and indeed indicates the law would be "stupid AF" to be that way in other countries.

Again, clearly USA here. USA laws apply.

Third, my comment clearly indicated that I was referring to other countries, so if your statements are only applicable to America's legal system, you are following up to the wrong comment.

Can you provide some examples of free and democratic countries where this is not the case, in the sense of private citizens not being allowed to take photographs of other people in public places? Examples like Google Street View don't really hold up when all of western Europe has (in the legal sense) accepted its use with specific restrictions which reflect the fact that Google can collect data in excess of what an ordinary person would be able to do.