I visited a major US city that had "vaccine passports" last weekend. It was an absolute joke. Since hubby and I are not vaccinated, we had to get rapid test results at a clinic just before we left. We had the results on our person and also pics on our phone. We traveled with a couple with vax cards.
In the places that checked, there was NO WAY anyone knew who we were, nor could they read the results, or the day of the test, as the pic on our phones were tiny and never were we asked to zoom in. Never once did they ask any in our party of four to produce ID to prove we were who the card/test said. On the last day, our 72 hour tests had "expired". Not one person in bars/restaurants/hotels caught it nor seemed to care.
It's a complete joke, just like everything else Covid.