Canadian law has no effect on US law and therefore is irrelevant to the discussion.
Ted Cruz isn't a NBC of Canada because Canada says so, Ted Cruz is a NBC of Canada because he was born in Canada. period.
Baloney. The citizenship laws of all nations has play in a citizenship determination.
When Cruz was born, Canada had a claim him because he was born in Canada of people who were legal permanent residents of Canada. He is not an NBC of Canada because other countries had recognizable claims on his citizenship.
When Cruz was born, the US had a claim on him by operation of an Act of Congress.
When Cruz was born, Cuba had a claim on him by Cuban law.
The US and Cuban claims stand in the eyes of all countries, with equal validity. It was only acts subsequent to his birth that made Ted more a citizen of the US than a citizen of Cuba. But we don't look to action subsequent to find NBC. We look to the circumstances of birth.