Visa needed to fly through United States?

Its called a "transit lounge" and most international airports in the world have one. People catching a connecting flight don't actually enter the U.S. proper by staying in the transit lounge, thus, wouldn't need a visa. Why would you need to go through customs if you're only catching a connecting flight? I would go back and ask your ticket issuer. They may have misunderstood your intention not to officially 'enter' the U.S. but merely to transit through. The other issue that your ticket issuer can answer is whether or not your infant needs an official visa to enter the U.S.or whether just identification proving that it is your child. If you're Canadian, I suppose that makes your child Canadian by default. Good luck!