Wasn't under the jurisdiction there of already defined by common law we were following and defined and solidified by the Supreme Court in Wong Kim Ark again matching the existing common law used by us?
Allegiance was already defined in common law as well, any foreigner arriving here that was not an invading enemy or foreign ambassador was a subject to our Sovereign and allegiance to our Sovereign's laws.
In English common law, the phrase referred to total and exclusive allegiance to the sovereign. This status, known as jus soli, granted subject status to anyone born within the King's dominion, provided their parents were not invading enemies or foreign ambassadors.
I think we need an amendment if we were to change the existing meaning.