That's your interpretation of jurisdiction (and many others state it that way, too). But there's no clear source for this interpretation, other than wanting it to be so. After all, "juris" refers to courts and the laws, so this is the most direct interpretation. Furthermore, the Constitution pretty well limits discussion of citizenship to the ability to vote, and the ability to run for office. Other than that, anyone (usually referred to a persons or people in the Constitution) were under the legal jurisdiction of US laws, And what other jurisdiction could there be, except being under the jurisdiction of our laws, civil and criminal?

I don't see how the "legal concept of a resident alien didn't really exist yet" really pertains. Only way around that is a constitutional amendment, that would state somehow that a "resident alien" now matters, presumably within the amendment that cancels birthright citizenship.