It seems people have missed what the proposed alternative is, so let me spell it out: it's about getting governments to SIGN AN INTERNATIONAL TREATY. It is NOT about having US (or anyone else) policing the rest of the world.
It's not fundamentally more dangerous than the few existing treaties of similar kind, such as those about nuclear non-proliferation. And obviously, all nuclear powers need to be on-board with it, because being implicitly backed by nukes is the only way any agreement can truly stick on the international level.
This level of coordination may seem near-impossible to achieve now, but then it's much more possible than surviving an accidental creation of an AGI.