Ted Cruz isn't a US citizen at all, much less a natural-born citizen. He was born in Canada to two Canadian citizen parents. His mother was an American citizen previously, but when she became a Canadian citizen before Ted's birth, she took an oath renouncing previous allegiances. That qualifies under US law as a renunciation of her American citizenship.Therefore, she was not a dual citizen; she was a Canadian citizen only.
So, Ted Cruz is pure Canadian. He shouldn't have been allowed to hold any office in the USA, not until he got his citizenship.