+1 on everything above, as I've also said this all before- it ain't news.
My last entrances to JFK from Paris (March) and UK (June) were just as QF described. I actively had to look for and seek out a Customs agent in March, and I was thrilled to do it. Not only added just 15 min, so I was STILL in my car while most of the plane was waiting for bags etc., but the Customs agent was actively appreciative of my looking for him. So much so that he declared I had the lowest possible amount due ( their calculations can be very elastic), and that I should just go now having filled out his form, and they would send me a bill ( I think the CC machine was out of order). Bill arrives exactly when he said it would, and for the amount he had "calculated" it to be- which again, was exceedingly below what it should/could have been- and I was done.
As of now- the duty free amount into the USA is $800 per person, but can be combined with a spouse/family member/ person living in the same household for a (usual) total of $1600.
here's the link the US Customs and Border Control- everything you could possibly want to know is there.
Have a wonderful and safe trip!