Both are equally correct, but "a lot" is not a very academic term, but is sufficient and correct. Perhaps: NYC has a multitude of cars. Or, There are very many cars in NYC.
Or In common speech, 'a lot' comes up, well...uh..., alot! In writing, it's fine for youngsters, but' many' or 'much 'seems more apt usage.
Technically, the teacher is correct. I had to see her alternative to understand why though. I don't think ANYONE else would notice.
The reason is this: In NYC, there are many cars. The cars are there, in New York City. The sentence your son created suggests that New York City OWNS the cars.
To prove the point, change NYC to something else. "My brother has a lot of cars." If the sentence was "NYC has really cold winters", or "NYC has a high crime rate" it would be fine.
So for you to say "NYC has a lot of cars" makes perfect sense. But trust the teacher on this. Even though your son's sentence makes sense in Conversational English, that doesn't make it Proper English.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.