I'm a U.S. citizen through my parents, even though I was born in New Zealand, where I've lived most of my life. I came to the U.S. to visit, and realized I'd like to spend more time here. So I made an appointment at a U.S. passport office, figuring it was time to get proof that I'm a citizen. But they told me I had to come back with a Certificate of Citizenship. I looked at the instructions for Form N-600, to get the certificate, and it says that one of the types of evidence I can present is a U.S. passport! This seems very circular – what's up?