Tediek, you need to get your PPL validated by the FAA. This will involve the Dutch authorities. You are then issued an FAA PPL "based on" your JAA PPL, meaning that your FAA PPL will be valid as long as your JAA PPL + medical are valid. This last bit of paperwork is done at an FSDO, which is a field office of the FAA.
You then do a Biennial Flight Review with an FAA instructor, which is the FAA currency requirement and consists of an hour groundschool and an hour in the air, and you're good to go.
All information here:
Airmen Certification: Verify the Authenticity of a Foreign License, Rating, or Medical Certification
If you have more questions, open a separate thread. It's not really relevant to the OPs problem.