Maybe I'm missing some prerequisite knowledge here, but why would I assume `flag="us"` is an emoji? Looking at that first block of code, there is no reason for me to think "us" is a single character.
Edit: Turns out my browser wasn't rendering the flags.
In Windows Chrome, it doesn't render the emoji for me. In Android Chrome, it renders a flag emoji - not the raw region indicators (which look like the letters "u" and "s").
In my browser (Firefox on Windows), the thing between the quotes in the first block of code looks like a picture of the US flag cropped to a circle, not like the characters "us".
Ah I see, I just opened it in firefox. It looks like some JS library is not getting loaded in Edge. The author was talking about "us", "so", etc. looking like one character and I thought I was going crazy, lol.
I don't think that's about a JS library. Firefox bundles an emoji font that supports some things -- such as the flags -- that aren't supported by Segoe UI Emoji on Windows, so it has additional coverage for such character sequences.
If it's Windows, it doesn't actually use flags for those emojis, it renders a country code instead. If it wasn't supported you would just see the glyph for an unknown character.
The reason was because they didn't want to be caught up in any arguments about what flag to render for a country during any dispute, as with, e.g. the flag for Afghanistan after the Taliban took control.
Do you have a citation for that? I suspected it was because of the political issues, so I tried hunting down the reason one day and came up blank.
[Microsoft had this same issue with the timezone map in Windows. The early versions were cool and had country borders, but then I think it was India/Pakistan threw a fit and it was simplified to take the borders out]
Edit: Turns out my browser wasn't rendering the flags.