I reckon quite a few countries with English as an official language will have "cop" as a nickname for "police" - even in places where their police culture might significantly different from US police culture.
Also, in non-English speaking places, there are usually long standing slang words of similar standing, e.g "flic" in French. The evolution of police novels is multi-linglua (Wahloo / Sjowall, Simenon) so reading "cop" in english is not a dead giveaway, though I understand the point having read through the discussion.
I was going to say that, but a little googling showed me the word “cop” is not of American origin.
Interestingly, in my native language (Hungarian) the word "kopó", which means a kind of hunting dog, used to be slang for a detective. I thought there maybe was some connection to "cop", but apparently it's just a coincidence.
Neither does 'Fall' (season), but in modern usage it all but guarantees the speaker is North American (or ESL and learnt it from them).