Would it be okay for another country to conduct such drone strikes on US soil? If not, which countries are allowed do do such things, and where, and why?
How can you prove that lives were saved by the drone strike?
The point of military action is that all other viable diplomatic options have been exhausted, and something must be done to stop an avowed enemy. We're not going to sit around waiting for known terrorists to carry out successful attacks on innocents before doing something to stop them. "Reflective contemplation is not required in the presence of an upraised knife." Once such military action is deemed necessary, the question then is whether a single drone destroying a few rooms and their occupants with zero direct risk to US troops is (or isn't) preferable to destroying several city blocks (at minimum) and their occupants with significant risk to our personnel. You demand proof, but only from a position of prejudiciously rejecting any given.