JFK airport in New York City is really overcrowded and the service has deteriorated. I would avoid using this airport as a point of entry to the USA. I have made several trips to Europe in the last few years, and have flown in and out through, JFK, Newark, Philadelphia and Charlotte. So far, I think Newark is one of the better choices. It is overused like most of the east coast points of entry, but at least its terminal is spacious, its gates are convenient and it has a reasonable choice of restaurants and shops. The customs and passport control facilities are fairly efficient. Unfortunately, the time from boarding to takeoff can be as much as one hour during the busiest times of the day.
JFK is one of the worst points of entry. It is terribly overcrowded. The gates are not conveniently located, and it is difficult to get from terminal to terminal with any speed. Delta has so many planes at this airport, that they cannot even get them near the gates. They use people movers to transport travelers from the aircraft to the terminal. It is not uncommon to spend at least an hour getting from your air plane to the passport control area. Some of the airport employees including the TSA security agents, the passport control people and the customs agents can be rude and inconsiderate. To be fair, I must also say that a few of those employees can be kind and considerate.
Philadelphia and Charlotte are mediocre. They are overcrowded, and takeoff waits can be quite lengthy, but their terminals are adequate. The passport control, customs and TSA security at Charlotte are rather slow and inefficient from what I saw.