Canadian laws will not be used to dictate to us who we can elect as our president. Just stick with our Constitution and don't let the Canadians confuse you. They can do what they want on their side of the border (except call us bad names!). The issue is not with Canadian laws, it is with ours. Cruz is a citizen by virtue of a law that did not exist in 1787.
You can't change the meaning of the words after the ink has dried.
I understand your point. But, then, Richard Nixon was born in Yorba Linda, California (which wasn't part of the United States in 1787). Maybe the term "United States" in "natural born citizen . . . of the United States" was intended to be flexible enough to include new states that might be added in the future. Similarly, maybe the term "citizen" in "natural born citizen" was intended to be flexible enough to include new circumstances under which someone can be born a citizen of the United States that might be added in the future.
But, of course, it's just another argument to pitch to the voters and their electors. Perhaps the more they hear and consider, the better will be their choices. ;-)