The current state of battery technology makes the reality of such a scenario much less likely than being illustrated here. The energy density required to fly a small device other a fairly large range just isn’t there. A tiny throw away drone with a small explosive, targeting and maneuvering hardware probably has a range of a mile or 2 unless it’s designed as a glider that’s being dropped from attitude. In order to execute an attack of this type you have to be in close proximity of the target. I.e. you’d have to fly a plane and drop a bomb of these over the target. Or find some other way of getting them close to the target before activating them. A Nuke would still be far more effective at just pure large scale damage unless of course you’re looking to kill the people while preserving the infrastructure.