It said: "...all children, born out of the king's ligeance, whose fathers were natural-born subjects, are now natural-born subjects themselves, to all intents and purposes, without any exception; unless their said fathers were attainted, or banished beyond sea, for high treason; or were then in the service of a prince at enmity with Great Britain."
I have never been a “subject”.
Neither of my parents were “subjects” to England or any other nation.
Blackstone was an English Jurist & Judge. Yes, he was an authority on English Law. Not US law, and they are not the same.
This is not as simple as you suggest. And I do not have the time today to find you the reference material to support what I said.