Like Cali, NY is oversaturated with orthodontists, but it's also saturated with people so the patients to doctors ratio in NY is probably the same as in rural areas. Oversaturation of GPs also means more referral sources. People in big cities tend to care more about their appearance than people in less populated areas. There are also more working adults (recently divorced men/women, parents of the existing patients, recent college grads with good paying job etc) in big cities who want braces. Many wear braces 2 or 3 times because they didn't wear their retainers.
It depends on how good are your clinical and business skills. People will line up to see you no matter where you are. Having a good reputation is very important.