It wasn't confusion but allusion. Gruber is sitting there pontificating about 'stupid Americans' whom he views as equivalent to Goober Pyle, himself doing something INCREDIBLY stupid, namely admitting his perfidy on camera. Gruber is the idiot here. Equating the two was the joke, effectively a pun-in-picture.
Apparently you missed it.
I, of course got it. I was being ironic. Sometimes that doesn’t carry through these threads. I thought your picture of Goober Pyle was hilarious. I was just going along for the ride.