Again, I'll ask - more slowly - show for me in the US Code, the US Constitution or in any legal holding (you know what "legal holding" means, right?) of a Supreme Court Case where I might find the definition of natural-born citizen. As best I can tell, "The Poste Mail" isn't any of those.
The Supreme Court said that the definition of NBC is extraconstitutional in Minor v. Happersett:
” ... all children born in a country of parents who were its citizens became themselves, upon their birth, citizens also. These were natives, or natural-born citizens, as distinguished from aliens or foreigners.”
This almost word-for-word from the definition attributed to Emmerich de Vattel in his treatise Law of Nations.
There you go.
The U.S. Code is not the dictionary for the Constitution.
The absence of its meaning in the US Code may bery wello mean that its meaning was well understood and not in dispute.
Multiple Supreme Court Justices have documented the meaning of the phrase in their writings. Their writings are more authoritative of its meaning than a U.S. Code that is absent of it.
I prefer the evidence provided by the writings of these Supreme Court Justices and other authorities throughout history documenting its meaning than the evidence to the contrary thet you don't have.