His mother was born in Kansas, making her a citizen from birth. Doesn't matter how long she lived in the US, though she did spend her childhood here. I didn't know there was a requirement for a natural born citizen to spend a certain amount of time in the US to maintain their citizenship.
McCain was born in the Panama Canal Zone, then a US territory, or under US control, to US citizens, so nothing to quibble about there. Ted Cruz, on the other hand, was born in Canada, to a mother who was a natural born US citizen. His father, on the other hand, was born in Cuba, as a Cuban citizen, and fought for Castro during the revolution there. Legally, therefore, he is a US citizen, through his mother, regardless of his place of birth. By the same token, it doesn't matter where Obama was born, as long as his mother was a US citizen at the time.
Regardless of political affiliation, if you accept Cruz's credentials, you have to accept Obama's. And if you reject Obama's then you have even less reason to accept Cruz's.