It doesn't define "bullets " either, but it certainly protects the right to keep and bear arms, the exercise of which requires "bullets."
Natural Born Citizen is an axiomatic extension of the founding doctrine of the US. It's called "Natural Law", and it was a "thing" in the last half of the 18th century. It was a very big "thing" back then.
And if the 1790 act chose to give a description of what a NBC was and subsequent acts never chose to rescind that definition I will go with the precedent.
“Natural Law” does not bestow citizenship on anyone. Natural law existed waaaaaaay before the United States was ever thought about.
The planets orbiting the sun is an example of Natural Law. The rising of the tides is an example of Natural Law. Natural law has nothing to do with the establishment of economic systems or geopolitical boundaries or the price of tea in China, as all of those are man-made and temporal and fickle, and can change on a whim. Natural Law is not so flexible.