Thanks for the fun quiz. I would argue that New York City has five boroughs. The sixth flag is the flag of the city, so kind of not in the category of borough flags.
Correct, sincerely I added the flag of the city for the mere fact of adding one more, and also because I was not very sure if it could be considered or not a borough more, (things of being Spanish and not understanding very well the administrative division of another country), even so thank you very much, I will specify it.