“The child of a citizen is a citizen” is not really right. US citizenship is derived two ways; by land (born here) or by blood (through parentage). Only the former is basically unconditional. The latter is subject to restrictions.
The rules on derivation of citizenship can be… complicated.
I'm trying to understand how it's possible to be born of a citizen on US "soil" and not have citizenship?
That confuses me. The child of a citizen is a citizen. Someone born on US soil is a citizen.
I feel like the article is missing something because it doesn't make sense.