The majority of our healthcare research, logistics, and environmental advancements, and most other aspects of 21st-century living can be switched over to alternative technologies that do not require computers. The main thing we will definitely lose is social media, which many people would be glad to see removed from our lives, as it provides shallow and addictive dopamine hits, much like cigarettes, while diminishing the amount of time left in the day that people get to spend together in person.
Moving to non-computer-based technological alternatives takes significant cleverness. The engineers of the analog electronics era were geniuses compared to us today, and we can re-attain that lost level of skill. I welcome the challenge.
Who's going to agree to take on all that cost for no good reason? Why incur all that cost, even if it was feasible, for a mere unquantified possibility of something bad happening. Even if there was a firm date and "bad stuff" readily understood, e.g., Skynet going self-aware sometime in mid 2037, then folks will just do the bare minimum to forestall it at minimum cost.
Social media is going nowhere, especially if it currently makes money, just because of some idea of it potentially being bad.
No one, not the most screen addicted teenager nor the smarmiest snake-oil beauracrat, is gonna stand by ANYONE that suggests we need to remove ALL computers from society. Even the people critical of AI and social media are more than fine with computers and smartphones.
Regarding enforcement: Semiconductor foundries are physically large and require extremely high-precision equipment and very pure materials. They can easily be detected and can be isolated via blockades. Once the global superpowers are on board with the Initiative, each superpower can enforce the ban within the territories of their sphere of influence. There is no motive to cheat, none, because this is a matter of our children's survival. Cheating on the ban even a little bit directly threatens the survival of your own children and grandchildren. Additionally, all of the superpowers possess satellite surveillance capabilities which can be used to track global supply chains and ensure everyone is being honest.
The most important thing is to prevent all new fabrication of IC's, but I believe that as a compromise, it is acceptable to "grandfather in" already fabricated IC's.
Existing computers and phones could be allowed to continue to exist for as long as they can be kept running. With careful stewardship of this resource they should probably last for several centuries, with batteries being swapped for new ones every few years. Current computers are probably not fast enough to run true AGI, so this should be an acceptable level of risk and makes the Initiative more palatable to society.
Moving to non-computer-based technological alternatives takes significant cleverness. The engineers of the analog electronics era were geniuses compared to us today, and we can re-attain that lost level of skill. I welcome the challenge.