In fact, the Acts and Resolves of Massachusetts shows that they used "natural born citizen" and "natural born subject" interchangeably.
Even President Washington was not immune to using the term subject.
In a letter to the Catholic clergy in the U.S., President Washington ended with,
"And may the members of your society in America, animated alone by the pure spirit of Christianity, and still conducting themselves as the faithful subjects of our free government, enjoy every temporal and spiritual felicity."
http://www.beliefnet.com/resourcelib/docs/97/Letter_from_George_Washington_to_the_Roman_Catholics_in_the_U_1.html
It is rather hard sometimes to break a lifetime of habit. LOL!
Thanks (again) for providing a link. This thread is just turning into a treasure-trove of information!