To be honest I have found JFK to be one of the fastest airports to process inbound international flights. I am usually outside the terminal heading for Manhattan having cleared immigration, retrieved my checked luggage and cleared customs about half an hour after the plane has touched down. I've had one international connection at JFK when I arrived from LHR and flew out to YUL with about an hour and a half between flights and even with a customs inspection and rechecking my bags I made it.