If you have American citizenship by birth, which Cruz has, that is sole allegiance to America.
My grandson is a citizen of America and England. In order to give sole allegiance to a country, he would have to drop one of those citizenships.
Dual Citizens are not Article 2 Section 1 Constitutional natural born citizens. Read these words by the father of the 14th Amendment VERY CAREFULLY.
“Every human being born within the jurisdiction of the United States of parents not owing allegiance to any foreign sovereignty is, in the language of your Constitution itself, a natural born citizen.” (Cong. Globe, 39th, 1st Sess., 1291 (1866))
If you owe or share allegiance with a foreign sovereignty, you are NOT a natural born Citizen eligible to be president. How can you be eligible for the U.S. presidency with a Canadian birth certificate?