Let's look at the animals 'Maus' used.
Mice -- Jews (nationality did not apparently matter)
Pigs -- Polish
Cats -- Germans
Frogs -- French
Dogs -- Americans (and the British?)
Again, these are just metaphors. Mice are vermin and pest animals no one is too bothered if they are killed. That's why the author used them to represent the Jews. Not because he or the reader thought that way about Jews, but because that's how they were seen by the Germans. The Germans are portrayed as cats. WHy? Because cats prey on mice. That's why the Allies were dogs -- a child could understand this because the mice <-- cat <-- dog relationship is common everywhere.
