The AI calamity that will kill off humanity (or at least our current way of life) is the massively increased output of greenhouse gases on account of the huge AI datacenter power usage, mostly fueled by fossil fuel generators.

This will speed up climate change and the mass extinction event already occuring. For lots of living species on this planet it is already too late. And instead of doing everything in our power to counter that, we are actively piling on top of the causes for it. All for nothing but greed.