The big question is: "Why did it take the USAF So Damn Long?"
In WW2 the USAF used AZON bombs, radio guided free-fall weapons that could only be steered side to side (Azimuth Only) against long thin targets such as bridges. Using two AZON control systems, they used war weary B-17's loaded with 10 tons of explosives against high priority targets, an effort that was not successful except for some impressive collateral damage. Aside from the fact that the Project Aphrodite hardware was cobbled together rather than actually developed as a "Weapons System" B-17's were not designed to dive into targets. The USN did the same thing with old B-24's, having a much more sophisticated guidance system using television.
The USAAF also tried guided glide bombs in the ETO but accomplished little more than entertaining German AA crews.
The USN developed the highly sophisticated Bat misile in WW2, a radar guided Fire and Forget air-launched weapon that was literally 20 years ahead of its time. It worked, and if the IJN had provided more suitable targets it probbaly would have been judged as devastating.
Postwar the USAAF and USN both tried copies of the WW2 German V-1, including air launched versions, but discontinued it. With even a modest development effort they should have been able to use the Bat and TV guided bomb technology to deploy both radar and TV guided long range pulsejet powered (note: we never got our working as good as the Germans) standoff missiles in time for Korea.
The USN did equip some of its unmanned F6F drones as guided missiles and used them operationally in Korea. Some sources even say that the Hellcats scared the DPRK so badly that they agreed to a ceasefire. Maybe they thought they were US Kamikazes.
In 1960 the USAF was using Ryan Fireby target drones for recon and was experimenting with equipping them with armament, but the armed option was not pursued.
So finally, in the latter part of the Vietnam War, ONLY 20 years or so late, they used PGM's. As for armed drones like the Predator, the CIA beat them to it and the USAF only adopted the weapon when the CSAF told them to get off their butts and do it.
It is AMAZING what pilots will do to avoid any competition from machines!
P.S. I have that book too, but have not read it yet lest it piss me off too much.