I don't know what the legal minimum connect time is from int'l to domestic at JFK, but 1 hour and 20 minutes is probably legal. As much of a nightmare as JFK can be, the last 2 times I flew in from TXL, I BREEEEEEZED through!! The first time, we landed at a remote area, used a mobile lounge and from the time the door opened, off loaded pax, drove the mobile lounge to the terminal, went through immigration, my luggage was already on the belt, went through customs, rechecked my bag, went through TSA security, the total elapsed time was 18 minutes. I realize that this is really an extreme case of good luck, but I wouldn't really worry about it, to be honest. Maybe that's just how I am. I'm sure that some people are more worry warts than I am! My theory is - If you miss it, they'll get you there somehow.