Cruz is a nice guy. He was a citizen at birth since his parents were citizens at the time (and the issue has been raised several times before). The constitution says “natural” (as opposed to “naturalized). Elsewhere it uses birth within the United States to indicate a person who can not be denied citizenship (presumably Congress could decide that Americans born abroad are
aliens – but they have not done so).
The issue is important to many Israelis who hold a very useful right to an American passport having been born in Israel to American citizens. They are currently natural citizens, and to not have to be naturalized in order to become citizens.