They (and the Asterix books) were pretty common in language learning classes in the US. Obviously, primarily French as that was the original language, but because both series have been translated into nearly every European language (and beyond) they are also useful for others -- we read translated Tintin and Asterix in my German classes as well.
What's interesting is that some of the Asterix were even translated in local dialects. It's the only comic I've ever read in Plattdeutsch (https://en.wikipedia.org/wiki/Low_German). We also read it in a Latin class because some of the albums were translated in Latin (nice break between trying to translate texts from Cicero)
