New York City is roughly 41° north of the equator, along the curved surface of the ball-shaped Earth. In order for the sun to be at the Zenith ... to be 90° above the horizon and shine straight down on New York ... the equator would have to be tilted 41° away from the plane in which the Earth's orbit lies. But it isn't. It's only tilted about 23.5° away from that plane. So the sun can never be directly overhead at any place that's more than 23.5° away from the equator.
