I must admit that I never watched the Blackadder series when it was made.
Maybe I was too busy bringing up a family or whatever.
However, twenty or so years later I discovered it and realised what I missed.
Here is a clip to show how to insult nationalities.
They insult the Russians, Americans and obviously the cowardly French.
Of course, the British insult ..... the British nations too

Here is a video I found that has many funny insults.