We will be arriving at 10:00am from JFK and then taking a train from the airport to Naples. How much time should we allow to get through passport control/customs? Looking at train schedules and trying to determine what train time we can make. Our final destination is Praiano, so if you have recommendations for that, please do tell! Thanks in advance.
Regardless I would not buy tickets that would not be transferable if you miss the train, and you really never know when a delay or line will stymie you.
What month? Until late October, you could take a ferry from Salerno (which you can also take a train to from Rome) to Amalfi, then switch to bus. If it's after ferries stop running, I would consider a private driver from Salerno--get the whole shebang of the coastal drive with a professional.
Veladelphia is correct. Don't buy your train ticket till you are at the ticket window in the airport or at Termini. We have been through Rome's airport maybe eight times. Generally it is close to an hour from landing. Sometimes a little less and sometimes more. One Saturday morning from JFK it was 3.5 hours. Two immigration officers and about five international flights arriving around the same time and no one was in a hurry. No way to accurately forecast.
Because US citizens do not need visas, you can use the passport scan. Look for signs to automated passport scan. Some kind rickster has a response on this but I can’t put my finger on it. I’ll post when it do. It’s relatively new.
You also have to factor in if your plane will arrive on time.
Our plan last fall was two hours late. I would buy the ticket at FCO train station whether the train departs the airport or Termini -- that saves you the long lines at Termini. (or buy on line on your phone). We used to fly into Rome to get to Florence and always did it that way so we had no time concerns.