That's a good question, and I don't know the answer. If the law makes me a citizen of the state my parents are a resident of, then I am the citizen of a state, and a citizen of the US.
Residence and sojourn can complicate the analysis. I would not definitively say that those circumstances preclude state and US citizenship being deemed to occur at birth. Canada's laws may have play too, especially if the citizenship of a child born there depends on the parents being residents there. Law of nations frowns on creating stateless babies.
I can’t see how a provision that was meant to reasonably keep out foreign influences due to a person’s birth, and was left intentionally vague so the public in close cases could make a judgment call on it for themselves, would out-of-hand disallow from being President someone accidentally being born in Canada because of their parents’ weekend trip.
That’s really looking at a law to the exclusion of its purpose, and as though it’s trying to exclude everyone it possibly can.
But it might exclude everyone it possibly could, and still a candidate could have been subject to a strong foreign influence in many other ways, while still being “natural born.”
From everything known about this provision, it wasn’t meant or expected to be the silver bullet for eliminating foreign influences.
It was meant to clearly disqualify people in obvious cases, mostly that they weren’t born here but were immigrants that naturalized. Arnold Schwarzenegger is an obvious recent example of someone who there was talk of amending the Constitution for so he could run.
But the fact that Cruz was an American citizen at birth, and that so much hair-splitting has to go into claiming that he was instantaneously naturalized at birth, and that there is so much debate about this and support for him being natural-born, tells me that he’s eligible.
He meets the minimum legal qualifications at least, murky as those are, and is eligible, and so voters and the public at large will have to decide if they think his circumstances impair his ability to be President.
So keep in mind:
1. His eligibility question has nothing to do with the black-and-white definition of “natural born,” which eliminates people like Arnold Schwarzenegger.
2. His eligibility falls into the gray area about “natural-born citizen” intentionally left in the Constitution itself.
3. It’s quite a matter for academic debate, and scholars come down on both sides. I also see, for instance, that PolitiFact argues that he’s eligible. In this case, a good clear argument for him being ineligible just doesn’t exist. Hence, he’s eligible.