My first US passport required only Naturalization Certificate. (last year)
And to renounce my birth country citizenship required whole lot of documents and $200.
Interesting.It seems possible to me that it was that easy for you because gaining citizenship probably involved the submission of many documents,one or more in-person interviews,etc which would have been on file somewhere in DC.Just a hunch on my part,I could be wrong.
May I ask where your from (meaning what country,not where you are in the US)? It's a personal question so it's obviously OK if you'd rather not answer.Just curious!