0. I've initially been ambivalent or even supportive of Apple on this, because much of the initial criticism was uninformed and easily refuted, or hysterical. But I'm getting around to this being a momentous blunder.
1. I understand Apple doesn't like to discuss its plans publicly, but rather present the final product when it is ready to ship. But if anything was a good candidate for one of the rare exceptions, then this, no?
2. Why announce unambiguously that this feature is "available" in the US only at first, in other words, can be enabled/disabled/configured per region? What is the plan when country X comes and says "fine feature you've built there, here's our list of perceptual hashes of illegal imagery, and the contact data of our competent authority to notify in case of matches."? Replying "ah, sorry, we can't" is not going to fly anymore, ever (!).
Even if they walk this back, what defence will they have left in the future if any government requires them to implement this odious feature and scan all images on-device and notify some authority if anything untoward (in that jurisdiction) is found?