I don't know for english world, but I can say that in France Mafalda was relatively well known in the 80s and 90s, since you could find Mafalda comics in every

I don't know for english world, but I can say that in France Mafalda was relatively well known in the 80s and 90s, since you could find Mafalda comics in every public library for example. However she was not very popular amongst french kids probably because 1/ it was complicated and filled with political satire that kids could not understand 2/ kids were not accustomed to "comic strip" style. Amongst adults, Quino was appreciated for Mafalda but even more for his other works (of which I am a huge fan)