US dub of "Henry's Cat"

I think you're a little behind. Four episodes from the US dub were released on VHS and uploaded to YouTube. These came from Series 3 and were aired on HBO. I think the PBS airings were from either Series 1 or 2 and used the UK dub.

I also saw a comment on a YouTube upload of the Series 3 episode "The Treasure Hunt" that said: "I knew I recognize this. This was the first episode of the series I saw on HBO back in the 80s".
Edit: The video has since been marked as "made for kids", so comments are now disabled there.

So this leads me to believe that we still have a bit more of the US dub that has yet to be found, and since the US dub contained two stories, "The Computer" may also have one as well.

Well, I still have them if you want me to reupload them. Did you try searching "Henry's Cat HBO" on YouTube?