Has any travellers had issues with the San Marino tourist stamp invalidating their passports or issues returning to the U.S?
Wasn't an issue because I knew that a souvenir stamp could be considered defacing a government document, thereby invalidating it. So I bought a postage stamp, stuck it on an envelope, and had that stamped instead. A passport is your most valuable means of identification, not a souvenir album. And it's not just US border control you need to be concerned with, but any Immigration official anywhere in the world who inspects your passport.
San Marino is an official country recognized by the UN. A passport stamp will not invalidate your passport or deny you entry into the US.
San Marino is part of Schengen and there are no border guards but you can go to the tourist office and get a stamp.
This reminds me of the days before Schengen. People would go to Liechtenstein to get a passport stamp even though the border guards were Swiss and you got a Swiss passport stamp. But people, including me, would go to the LIechtenstein tourist office for a Liechtenstein passport stamp.
Never had a problem.
Except the San Marino stamp is clearly marked as a tourism stamp. Not an Immigration stamp.
It is considered a tourist visa to San Marino.
It says "Visto Turistico" which means Tourist Visa. And since the tourism office is part of the San Marino government, it is considered official.
Now, if you got a "Checkpoint Charlie" stamp, it could cause problems,
I have never heard of anyone getting in trouble with a San Marino stamp. If it did cause problems it would be all over the internet. Do a Google search.
I got my passport stamped there 38 years ago or so and never had a problem