Here in the US…
Legal use, such as a corpse appears with no name, someone in hospital (or TV hospital drama) has amnesia and can’t remember his name, he’s “John Doe”.
Casual conversation, your average person sometimes in a derogatory way is (a) “Joe Schmo”.
The average person, esp. perhaps in a political context, might be “John Q. Public” or probably less frequently “John Q. Citizen”.
Average person for an example in casual conversation such as storytelling is likely “John Smith”.
For female counterparts, equally (traditionally) common female names like Jane or Mary are substituted. Sometimes you see something like a Suzy just because it’s a little more creative.
But presumably an alpaca herder in Peru doesn’t spend much time considering what “Joe Schmo” thinks?