The last news I got is that the Pentagon said the ground forces, Afghanistan, called in the drop.
If true (and if this day and age of spin, who the heck knows?) that makes this technically "close air support" and not "an air strike" but unless one's been in the business one misses such distinctions.
From what I remember of close air support called in by ground troops: the general rule on "is this a legit target or not?" is that the ground commander has to determine that before the call for air launched weapons arrive.
While I have no idea what RoE the Afghan forces are under, I suspect that they are somewhat like our own with the past 10-14 years of training/liaison and such.
But nobody wants to blame that local guy, they want to blame the Americans because it's fashionable.
Just a quick note: form the air, most hospitals look like any other building.
If the ground commander did not identify it as a hospital, and the crew in the aircraft didn't have info that it was, and that was the grid where the weapon was called for ... what a mess no matter how you look at it.