I think most non-Americans would have thought it bizarre if an American reporter asked them if they were intending to join an American sport when they were finished their Olympic career.
I don’t think Usain was necessarily being disrespectful, as much as he was simply taken back by (in his POV) a bizarre question.
I’d have to see the video tape to be sure on that point, but that is my suspicion, because I would probably have the same reaction in that situation.
It would be like an Irishman asking an American athlete if they were interested in playing Gaelic Football when they are finished.