That's not what's being asked. There already exists software, and optional functionality on OSs/routers/browsers, that allows parents to restrict what sites can be viewed. This software covers more sites (and offer greater customization) than proposals involving sites verifying ID would, since:
* The software can trivially add sites to its blacklist regardless of whether they're outside of jurisdictions that would require ID verification
* Sites are more likely to identify themselves as pornographic than to implement ID verification, since it's a significantly smaller burden
* Small/obscure sites that could fall under the radar with non-compliance on ID verification can still be blocked by the software with statistical/ML methods
* For young children a whitelist of known-safe sites can be used
Neither approach is perfect. With ID verification, a child could use a free VPN to bypass it, or be shown a friend's older brother's ID. With filter software, a child could borrow an unfiltered device and find an unfiltered Internet connection to use it on. The question is: would ID verification be better to such an extent that it justifies the privacy invasion and increased risk of fraud, blackmail, etc.? To me, it seems substantially worse than existing solutions.