The author of the joke doesn’t really matter here; the point is that it’s funny, period. I’m not sure how you can see a mockery of any country in a joke that would work with literally any important person in any country.

In that case there'd be no need to mention reagan at all? most of the "Soviet" jokes people tell seem to be made up anyhow.

Comedy is subjective.

Try telling a sexually charged joke at your place of employment and see what happens.

World leaders freely slandering other countries like this is shameful, and not what you expect from a "world leader".

There’s nothing slandering here. As I wrote above, the joke could work with literally anyone.

> "jokes" at Russia's expense

I'm not seeing it. That joke could just as easily be told for any other national leader and it would still work.