Following up, should anyone care. I asked DH about his “birthright” as it were. If I understand correctly, and I may not, as part of the SOFA (status of forces agreement) he was considered a US citizen and was born on a military base hosted by another country (in, at the time what was more of a quonset hut than a hospital). He doesn’t recall if, at the time, he was considered a dual citizen but seems to recall having to makes some decision when he turned 18. But only had a US passport.
Carry on…