The US has been using drones for a long time.  The Ryan Firebee performed thousands of missions in Vietnam, Laos and around Chinese waters during the police action otherwise known as the Vietnam War.  They were very successful in their photo and radio reconnaissance missions, but were susceptible to anti aircraft and missile fire.  Some were flying preprogrammed missions, and some were flown by a tv link from a hovering C-130.  They later became invaluable in detecting surface to air missile sites (The infamous Sams) and getting intel on their capabilities.  They could only do this, however, by becoming a target, which shortened their lives considerably.  Later, they came to even emulate F-4 fighters to really encourage the North Vietnamese to use up their Sams.

C-130 carrying Firebees

There are some wild stories about their involvement in the war, and Tom Cooper (Air Combat Information Group) contends one of the Firebees even became an ace, accounting for 5 enemy aircraft coming to grief trying to shoot it down.  Whether that's true or not is difficult to determine as there are scant details of the drone involved.  What does seem to be true is that at least one North Vietnamese pilot was killed, Mig 17 pilot Luong Duc Truong, taking out a drone in 1971 which is detailed in István Toperczer,s book, "MiG-17 and MiG-19 Units of the Vietnam War".

Firebees in hanger