So if your parents travel into Canada for the weekend and you’re unfortunately born there, you’re ineligible to be President.
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.
Not if both parents are American Citizens at the time of your birth!