As TransportEng mentioned, we have a terminology issue here.
In general (but there are 'grey' areas):
Drone: Dumb flying vehicle that is either radio-contolled or has a simple programmed flight path. Usually intended as an aerial target.
RPV: Remotely Piloted Vehicle. A glorified radio-controlled aircraft. If the signal is lost, probably so is the aircraft.
UAV: Unmanned Aerial Vehicle. An air vehicle that has some capacity for auto-flight and navigation (but is usually controlled by a human operator, particularly for landing).
UCAV: Unmanned Combat Air Vehicle. An air vehicle that can be controlled from the ground but has a capability for auto-flight and navigation, but is also equipped with attack munitions (i.e., as UAV but packs a punch).
Note: There are other classifications for rotorcraft etc.
As far as drones are concerned, pretty much all nations build them. As far as UAVs are concerned, the key nations are the US (wow! that's a shock), UK, Sweden, Israel, France, Germany, Italy... err, I could go on, but my keyboard only has a 1 million keystroke guarantee...
In summary, you can design and build a drone in your bedroom. You can design and build a UAV in your garage. And, as the Predator has shown, you can do the same stuff in the same room with nothing more than a munitions licence and a few smart people... The US is leading this field (in the public domain, at least), but the other nations aren't too far behind. Watch Dassault in the next few years to see what comes from 'across the pond'.
As a last thought, we are already flying UAVs in the civil air system; it's only a matter of time until we start flying commercial UAVs (I'm talking freighter and, eventually, passenger services), so a couple of 'drones' over Iran shouldn't really be too surprising...
The definition of a 'Pessimist': an Optimist with experience...