Mencken's whole schtick was to be a populist intellectual. At one point he was so famous that a letter from Germany simply addressed "Mencken, USA" got delivere

Mencken's whole schtick was to be a populist intellectual. At one point he was so famous that a letter from Germany simply addressed "Mencken, USA" got delivered just fine. His usual essays and reportage use more elevated language than this. IIRC he wrote this to make the point that "American" was a separate language from "English", and stuck in every Americanism he could think of. The median American today probably speaks better English than back then. Literacy is up, radio and TV are universal so you don't just hear people on your block, fewer of us are recent immigrants, etc.