He actually learned German well enough to have appreciative audiences in Germany, but he also knows how to make amazing comedic essays on many topics. He did plenty about US-specific topics, and about French too, not just about German.

Which gives us Hitler memes where they audibly says German words that are very similar to their English counterparts, but the /funny/ subtitles is just a Beavis and Butthead level joke.

Doesn't work as good if one has ears.