Related: did any country perceive themselves as being at a technological advantage in some area and makes economic, strategic and tactical decisions accordingly?
I can't think of any 'clear' technological advantages, though certainly some technologies were implemented better, or sooner, in some countries than others.
The obvious exception was demonstrated on Japan in August 1945.
Thoughts which come to mind: M1 Garand rifle for the US, best rifle of the war, most important factor being the rifleman. Other countries such as USSR did produce semi-autos throughout the war, but only the US had such rifles issued to all troops.
A related one is the use of the 'walkie-talkie', the US had good hand-held radios giving them a marked communications advantage.
radar comes to mind as another, particularly with respect to the British air defenses and American naval gunnery. That said, the Germans fitted radar to a number of their ships as well. The difference there being that the German navy became something of a pointless entity, so there was little use made of it, and so we don't associate it with them.
Speaking of radar, the VT fuze for artillery has to get a mention. This US invention made artillery substantially more effective.
The Japanese had some serious anti-ship torpedoes (Which also had the slight flaw of sometimes blowing up the ship they were mounted on), whereas the US Navy torpedoes of the early war were particularly useless until the problems were solved. Then again, the night torpedo engagements that the Japanese had envisioned almost never happened, and the US fixed its issues without too much trouble.
There were certainly other points of relative advantage between different countries. The US built better jeeps and trucks than the Germans, the Soviets built great attack aircraft, Americans better bomb sights, and so on, but they strike me as being more cases of better applications of design as opposed to anything really 'new' and 'technological.'
The atomic weapons used to force Japan's capitulation are an example of United States' technological, and unrivaled at the time, superiority.
Same can be said about American long-range strategic bombers that brought the Axis economies to a halt.