This is a really dumb argument.
If you think it is a dumb argument, you aren't seeing the ramifications of it. The Liberal argument is that a fetus is not a person TIL BORN. The Jus Soli argument is that a fetus is not a citizen TIL BORN.
The Pro-life Argument is that a fetus is a person from the moment of conception. The Jus Sanguinus argument is that a person inherits their characteristics of citizenship from their parents at the moment of conception.
The Liberal Pro-Abortion argument shares a "qualification threshold" with the jus soli argument; That being Birth.
The Conservative Pro-Life argument shares an inherent characteristic of being a person with that same characteristic of being a citizen; by virtue of the parents passing on this characteristic.
And if it was born on an alien spaceship, it would have the citizenship of whatever planet the ship was from
Another dimension where they don't use planets. And where every molecule is the result of one shared multitasking particle. :)
The point is to boil down the "place of birth" argument to it's bare minimum threshold, and then show how silly it is to base citizenship on this minimum threshold. Citizenship ought not be decided by the few seconds or minutes it takes for the head to emerge, it ought to be regarded as a characteristic inherent in the child because of inheritance from the parents. It is the more logical way of looking at it, and it is consistent with the Pro-Life position.
What if the parents are from two different countries?
If you want to change the interpretation of the Fourteenth Amendment have at it, but this conception nonsense is unhelpful.