[null and void]

Yes. IF you already know a country is banned you can find out it is banned, or you could go through all 190+ countries one-by-one to find out which ones are banned.

I was looking for (and was sloppy in not mentioning that I was limiting my search to that angle) a list of banned countries. I couldn’t find one.

[Bubba Ho-Tep]

There's only one banned country: Cuba. Heck, you can travel to North Korea if you want. The NoKos won't give you a visa, but the US government won't stop you.

The fact is that travel bans are, legally, sanctions against the foreign government and are under the aegis of the Treasury Department.

So, back to the original question: Do you have any real evidence, other than more blog posts, that travel to Pakistan was forbidden in 1981?