This is one of many reasons why America's birthright citizenship is an incredible optimization: most people can prove they are American with a single document, a birth certificate.
Back in the 2000s, the Justice Department prosecuted someone for a terrorist offense. They researched their birth and found out their parents were technically diplomats of a foreign country.
It was a weird case, because the parents hadn’t actually been working for the foreign embassy for a while, and didn’t know they still held diplomatic status when their daughter was born.
They had entered the US as diplomats and shortly after decided to go local. That was probably their plan all along - lots of diplomats from third world countries do that.
It was a huge shock.
Kind of a “surprise, you’re not actually a citizen, even though both your parents and all your siblings are!”
