alt Hacker NewsWith software it's trivial to have a switch for "California compliant" mode, but in any case, that makes it clear that such criticisms should be directed at California. Other (generally "red") states already had a more reasonable solution: make the sites offering the restricted service liable for their actions just like other businesses.
The problem is that you could face liability if you do business in the United States and permit a minor in California to use an OS in non-California-compliant mode. If you're an "OS provider" in Wichita, KS, California will find that its jurisdiction still applies because the minor was in California and sue you in its courts. If you fail to turn up that's a judgement for the state by default. (And if you do turn up, it's a judgement for the state as soon as they prove a kid ran your non-age-checking OS.) And, thanks to the "full faith and credit" clause of the Constitution, California will be able to collect on its judgement against you in Wichita.
Hardware vendors are not going to want that kind of liability, in California, Colorado, New York, or anywhere else. So they will switch to selling hardware with locked bootloaders and only allowing approved operating systems within that locality (which for end-user PCs will mean pretty much just Windows). There is still foreign hardware, but those chinesium PCs are going to be confiscated by ICE unless the Chinese manufacturers also play ball.
Besides all this... federal legislation is coming.