Ted Cruz was born in Calgary, Alberta, Canada. His parents were both U.S. citizens who were working in Canada at the time. His mother was born in Delaware and his father immigrated to the U.S. from Cuba. The general consensus is that Mr. Cruz is a natural born citizen. As is the case when U.S. citizens are born in another country, Ted had dual citizenship. He's given up his Canadian citizenship.
I have three grandchildren who have dual citizenship, German and U.S. Only one of them was born in the U.S.