I'm a U.S. native speaker. "Drop a clanger" is _completely_ unfamiliar to me. I agree with Randy, "I put my foot in my mouth" is the first thing that comes to mind. A variation that's become popular, for someone who is always putting their foot in their mouth, is "he has foot-in-mouth disease" (a play on the real cattle disorder, foot-and-mouth disease). "Pop over" is occasionally heard in the U.S. Much more common are "swing by" and "drop by." "I'll swing by the supermarket and pick up a few things." "Swing by" implies a quick visit, leaving quickly after arriving. For a longer visit, we say "drop by." "I'll drop by your house and we can go over the plans." I have definitely heard "stick your oar in," but much commoner is "stick your nose in" (meaning to express an opinion where none was request." Another is "to butt in," which as far as I know is _not_ vulgar. (I just checked a dictionary and it lists it as a phrasal verb and doesn't label it as slang or colloquial). A person who makes a habit of butting in is sometimes called "a buttinsky."

These may not be the best, or even the only, examples, but here are my suggestions for American English equivalents: "Drop a clanger" = "sticking your foot in your mouth" "Pop over" = "drop by" (although I would say that "pop over" is also used in the U.S., but more likely as "pop in" "stick your oar in" = "stick your nose in" / "butt in" There may be other American sayings that would work, as well, but these are the ones that come to mind at the moment. I hope that helps.

Yes, "I'll pop over to the supermarket to pick up a few things" is fine. 'pop down' would probably be more natural in most cases. Dan and Randy have given some good options. 'Drop a clanger' can also mean to fart, here at least.

Hello! I'm from the US. I've never heard the first or third expression, but people do sometimes ay "pop over" someplace, exactly as you used it. ex: I will pop over to his house after work. Overall I think these are less frequently used in American English