First of all, he mentioned he has lived all his life in America so I'm not sure where you're getting the notion that his English is a fake imitation.
Secondly you haven't heard him speak, so how did you manage to make judgements on his accent?
Thirdly, he never intended to flex about being American or living in America. It is the incessant arguments from your country people trying to deny that he lives in America that made him post photos to confirm that he actually lives in America and is American.
I appreciate that you sound like an objective person not fueled by emotions than most here but kindly follow the whole stretch to understand where all this came from.