“If a TV channel shows an X rated movie, they need to ensure the age of everyone watching.”
First, the networks would not be able to sell advertising time for X rated programming.
Secondly, TV networks cannot be responsible for everyone watching a TV just as auto companies cannot be responsible for everyone who drives their cars and firearm manufacturers cannot be held liable for everyone who uses their guns.
The latter are not pushed into households. If the gun manufacturers delivered guns to someone, they are obligated to find out if the recipient is old enough to acquire the weapon. It’s the same with car dealers. They don’t drive out to a house and deliver a car to a 9 year-old.
Hoisted on your own petard.