I think you're right about TSA. It's not really their job to worry about that stuff is it?

Here's a blurb from the US Dept. of State web site: "Be aware the United States does not have exit controls or require two-parent consent for a minor to travel across international borders. Law enforcement may be unable to prevent an abduction without a valid court order clearly prohibiting the child’s travel outside of the United States."

And even more info: https://travel.state.gov/content/travel/en/International-Parental-Child-Abduction/prevention/prevention-faqs.html

It looks like there are steps that a parent can take ahead of time to help prevent an abduction from taking place.