They probably didn’t air internationally because they show words on the sign. Or are there sight word segments that have aired internationally (it would be hard to replace the words being spelled)?
I looked at the “what links here” and so far the wiki doesn’t know of any airings past season 3. The yes segment is noted as being in two episodes so far and the no segment in three so far. Looking at the script, I don’t notice anything that would make the segments objectible (not more so than any other Kermit and Grover segment that was circulated for years), so if they were both pulled from the show then they must not have taught the kids that well.
Hopefully it won’t be long before we see if either aired after season 3. It’d be interesting to know if they ended up airing past season 4, and I really don’t expect either airing in seasons 14, 15, 17, 18, or 19 (was one of those seasons recently completed on the wiki?). And of course they might have aired in episodes without being in the scripts used for reference (I doubt they’d be in a whole lot of episodes despite not being in those scripts), maybe they were in some of the scripts that definitely aren’t the final aired versions.
I think those two skits used to be high on my wishlist for whatever appropriate DVD release (though in my mind, I’d usually only wish for one of the two per release), but in recent years I had most enthusiasm to see those (but if I heard they were online I’d probably watch as soon as I heard). When Toughpigs did that 50th anniversary survey and asked what we’d like to see on a possible DVD release, I don’t think I put either on my wishlist.