This is getting to be more fun than I thought it would be. Ted Cruz is a natural born American citizen blah blah blah
. But because he was born in Canada he's actually a Canadian citizen too. He's a dual citizen. This is the same as if a couple of French expats were living in the US and had a child and then returned to France. The child would be a French citizen but also an American citizen, simply by the fact of being born on American soil and whether or not that child ever took any active steps to exercise that citizenship.
After producing his birth certificate yesterday, The Dallas Morning News pointed out that Cruz is actually a dual citizen. At first Cruz and his staff appeared to deny that he is a dual citizen. But in a statement just released from his office, he seems to have come around to the fact that he is in fact a dual citizen and says he is willing to renounce his Canadian citizenship (and presumably any loyalty to Canadian head of state Elizabeth II), if it's true.
To renounce his Canadian citizenship, Cruz simply needs to fill out this four page form and pay $100.