Hmm I knew the one with the brahminesque Hitler/Hirohito from an history manual in middle school...
I remember an italian one depicting a thug-looking american soldier - well pilot, if I remember correctly, a thompson in its hand, with the american flag tied like a scarf around the neck.
Standing on a pile of debris and corpses,
in a pose not unlike the artwork from Fallout 1 with the vault dwellers couple... (well, sort of).
Edit : found it !
From the page of answers.com, the translation goes as this :
" The inhumane crimes of the gangster pilots exclude for ever the US from the commonwealth of civilized states ".
As a bonus, the webpage cited this website as a source :
http://www.fronta.cz/sekce/propaganda-plakaty-letaky-druha-svetova-valka
From what I can phonetically read, there are soviet ones, german, spanish (or not. "Spojenecké" ?), tchecoslovakian (sp?) and some various ones.