No - each terminal at JFK is stand-alone with its own CBP/Customs clearance facilities. So, upon exiting your AMS flight, you will be in the secure T4 transit arrival floor that empties into CBP/Customs. You will need to clear and enter the US, retrieve any checked luggage, and then exit the terminal. T1 and T4 International post-arrival meet-ups are only possible curbside, a good place would be the arrivals hall of T1 or the AirTrain station of T1 (you will need to take the AirTrain to get from T4 to T1.