Grocery store clercks not speaking english

Hi, i’m a northern european who visited Miami last spring and there was just this weird encounter that left an impression on me. I went to a smaller grocerystore in Miami Beach and the clerks there didn’t speak any english AT ALL. Like i asked for a spoon with my bread pudding and they started to tell it in spanish. Same thing in the check out, they did the counting in spanish ect. lol. I was just wondering how is it possible that people in USA, who work at a store, don’t speak ANY english at all? In my country even all the immigrants speak at least some english if not my country’s language. How come you don’t learn the most common language in the world while living INSIDE it’s country?