I am thinking to fly to Punta Cana, Dominican Republic, from NYC. How many hours do I need to be to check in before the the plane takes off?

3 Hours.

3 hours is the standard

I think the required arrival time to JFK Airport for International flight check in is minimum 3 hours. It use to be 2 hours prior, but that is long gone. The lines for the TSA Security check points in Terminal 4 is very very long especially from 5 o'clock on in the evening, because there are numerous flights departing for all points of Europe. The lines ran the entire terminal several times and back.

I say it least 2 hours in advance, to be on the safe side

3 hours for any international flight