This is my working assumption for all those teenage dystopias.
Hunger Games? World outside the US is fine. Better, now that the hegemon is more interested in watching it's own population murder each other for television ratings.
Don't want me making that assumption about your story? Maybe mention anywhere outside the continental US at least one [1] time. At least Handmaid's Tale acknowledges Canada. And I guess heaven forbid Mexico ever get a mention.