Clearly and likely indisputably that child would be an American Citizen. I also believe you would be responsible enough to fill out the proper paperwork and obtain a Consular Report of Birth Abroad so that you would have something besides a Canadian Birth Certificate and an assertion to prove it. Or, immediately obtain a Passport for the child via the same process.
These things are also done post facto up to the age of 18 years.
But, did the Cruz take that route...or just go to Texas 4 years later and start living a normal life?
We should require documentary proof for EVERY POTUS candidate.
If you read into the ‘Marshall Report’ this is the issue: “He did show his Canadian Birth Certificate and his paper denouncing his Canadian citizenship, but he has not shown any consulate papers. That must be what he has sealed. So if Cruz will just show proof of the proper papers there should be no problem. But, so far he has not and avoids the subject when asked.”