Priority Pass does not provide any access to Delta, American or United lounges. They are in the business of allowing lounges to monetize their excess capacity, and those airlines do not have any these days. Mostly you will find lounges operated by international carriers which have only a few flights per day, or independent lounges. Priority Pass also offers benefits at some restaurants, often in airports where they do not have lounge partners, but note that Priority Pass memberships sponsored by American Express and Capital One do not include the restaurant feature.

American Express Platinum ($695) provides a limited number of visits to Sky Clubs (when flying DL), plus their own network of Centurion and Escape lounges, plus Priority Pass. Read here: https://global.americanexpress.com/l...-platinum-card

Some credit cards issued by Bank of America, Capital One, Chase and US Bank offer versions of Priority Pass. Read carefully, the details differ.