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Probably goes under Artistic License – Linguistics.
That's what I was thinking, but was sure I'd seen a more specific trope at some point. Cheers!
Could be a bit of the recently renamed Creator's Culture Carryover - the description mentions "vernacular" as an example.
I think that's the one I'm looking for. Will add it in now. Cheers!
Seconding Creator's Culture Carryover, and adding Separated by a Common Language for more general examples of this sort of small-but-noticeable phrasing and term difference.
Looking for the trope where non-American characters use American terms when it wouldn't be realistic in reality.
For example, in Knock at the Cabin an Edinburgh-based nurse says 'parking lot' when they would have said 'car park'.