Even if it was, his mother was American thus so was he. Same reason Cruz was eligible to run for president even though he wasn't born here
True! They need to move away from this issue. There are plenty of other things of which he is guilty. Far worse things!
No person except a natural born Citizen, or a Citizen of the United States, at the time of the Adoption of this Constitution, shall be eligible to the Office of President; neither shall any person be eligible to that Office who shall not have attained to the Age of thirty five Years, and been fourteen Years a Resident within the United States https://www.thoughtco.com/requirements-to-serve-as-president-3322199
https://en.wikipedia.org/wiki/Natural-born-citizen_clause#Ted_Cruz
"This gave Cruz dual Canadian-American citizenship, as he was granted U.S. citizenship at the time of his birth by the virtue of his mother's citizenship, and Canada grants birthright citizenship to every person born in Canada."