Looking at the official Website there are a few different pass types. We plan to go to the main park multiple times during our visit. So, on the "My Pompeii Card" seems like the best deal.
On the website there is no mention of citizenship restrictions that I can find. . Nor information on how to actually use the pass. Do we still need to make timed ticket reservations?? Do we just show up at any of the sites listed whenever?
Pompeii Plus : valid for the Ancient City of Pompeii and suburban villas: Villa dei Misteri + Villa di Diomede + Villa Regina in Boscoreale with Antiquarium
Pompeii Express : valid for Only the Ancient City of Pompeii without suburban villas.
Pompeii 3 Days : valid for 3 days for one entry to each site (Pompeii Plus + Oplontis + Villa Arianna + Villa San Marco + Libero D'Orsi Museum + Shuttle)
My Pompeii Card : card valid for one year for visits to all sites + shuttle