JFK is a hit or miss. Depending on what time of the day you arrive, customs might be very busy or not. I once made it through customs in 10 minutes. Another time it took me over two hours. I'd suggest you inform the flight crew that you have a tight connection so that you can maybe exit the plane ahead of other people. Normally, you always have to clear customs upon arrival in the U.S. even if you have a continuing flight no matter where. After passport control, which takes the most amount of time, you simply collect your bags and walk through customs. Then drop off your bags at the bag drop area. That usually does not take much time. Then you will have to proceed through security again, which might cause a delay. Mind that you have to be at your next flight 15 minutes ahead of the departure, so you will have only 45 minutes to go through customs and security. It is doable unless you are traveling on a peak travel day during peak travel time, in which case you will most likely miss your connecting flight.
JFK is a hit or miss.