Most people probably haven't used or seen teletext in years, but I'd expect people to know what it is anyways because there's cultural references aplenty.
It was never really a thing in the US. There were a couple of short-lived attempts, but none of them ever caught on, and receiver hardware was rare.
Nothing there, but a page 100 telling you that there's no teletext, but page 888 still has subtitles on it.
1. AFAIK NTSC doesn’t support it, so North America never had it. There were equivalent standards but not one universal one to unify around.
2. Are there that many cultural references? I’m struggling to think of many that I saw growing up and I’m in my thirties. It existed (and I used it a lot!) but it wasn’t exactly part of the cultural zeitgeist. The internet had already taken over.
They have now transitioned to the web.