At least at CDG when you arrive you can go to the *A lounge before going through immigration. Was nice to do that arriving on TG from BKK to shower and freshen up and then make my way to the SAS lounge.

But ya...at JFK you're stuck with your terminal.

Only real lounge hoping that you can do would be Air India to Swiss in T4 and if you are flying NH out of T7 you have access to the BA lounge but could also visit the UC (no idea why you'd want to).