Just do what the European Union does already.
A Digital ID you can buy for a few bucks where you confirm your identity with your electronic device and after your age is verified your Digital ID information disappears from your local device after age verification is completed.
I imagine you can implement a similar system with the state's DMV where you buy a Digital ID from your state's DMV and use that to have full access to the Internet after your operating system of choice confirms your age and the information is deleted from your machine afterwards.
So the burden would actually lie mostly on the government to keep people's data safe because should a state's DMV database get breached then here comes the feds and look at who did the breach and which online communities are distributing said data breaches.
So in this hypothetical scenario, the states offering digital IDs would be considered government property and any threat actors that gain illegal access to said digital IDs would be in a shit ton of trouble because that would be a government database being the subject of concern. So if Jersh or any Kiwis think they can get away with it, the feds will knock on their front doors and ask the hard questions on how they got a hold of that kind of information in relation to government property. Just look at what happened to the guy that hacked NASA because he wanted to see if the American government knows anything about aliens.
And feds do not have a sense of humor because "We do a little trolling" isn't going to work on them.