I think, just plain old blind spot. He has tended to the overconfident, the proud. He might have gotten this from the way his dad treated him, with these spiritual proclamations of success.
The actual Christian model is that of the suffering servant. Each is willing to suffer to help the burdens of others, and will be rewarded with joy for this suffering. That’s what puts Christianity ahead of all other world faiths if it is done right; if done wrong it becomes an ugly clump of presumption and loses its attractiveness compared to other possible belief systems.
Cruz? I don't find the proposition tenable, that he believes he is qualified. He is an exceptionally skilled lawyer, and he has enough savvy to test his assumptions on important questions. Plus, he seems to be "accidentally" hiding (or not fully and forthrightly disclosing) more than his birthplace.
But, I will concede that you may be right. That on this issue he really didn't recall or associate any legal significance to being born in Canada and living there for his first four years. I have no doubt he considers himself 100% American, and I see him as 100% American - same way I see naturalized citizens.