The 1942 book Victory Through Air Power said the Allies should be focused on air power when invading Europe: conventional wisdom said otherwise. Walt Disney read the book, believed it, turned it into a documentary, and that film convinced FDR, who convinced Churchhill, et al.
I have no idea what people think about this, other than that it's weird that Walt Disney's view should have any bearing in how to fight a war. Was air power the better way to go?
Aerial warfare was developed on the go during WW1, with the pressing needs of the war taking precedence over formulating a larger doctrine. In the 1920ies, a group of people including Giulio Douhet, Walther Wever, Billy Mitchell and Hugh Trenchard advocated the use of strategic boming as a decisive weapon in future wars.
Tactical bombing is used to support ground forces directly, i.e. as "flying artillery". Strategic bombing aims to attack the enemies capability to wage war directly by attacking means of production, the infrastructure or the political and military command.
The idea of strategic boming gained a lot of traction in the UK and the US, much less in Germany and France. The UK and the US both started developing long-range bombers like the B 17 or the Stirling in the 1930ies. Both nations expected strategic bombing to play an important part in coming wars even then.
The US entered the war late in 1941. By mid 1942, the RAF was already engaged in a massive strategic bombing campaign against Germany. For example, on May 30., the first "1000 bomber raid" was flown against Cologne (Operation Millenium). As the Walt Disney movie was released in 1943, it is safe to say that the allied decision to focus on bombing germany had been made well in advance and without regard to the movie.
To the second part: Were the allies right in focusing on air power?
After the war, an extensive evaluation of the bombing campaign was done, which led to the "Strategic Bombing Survey". The experts came to a favourable conclusion, but did note several shortcomings.
A fair assesment would probably be that the strategic bombing campaign helped the Soviet Union defeat Germany, but could not have decided the war by itself. The Soviet Union would have preferred a sooner invasion (as noted by Valentin Falin in "Zweite Front").
Finally, the western allies never focused on aerial warfare only. They did wage war in northern Africa, Italy and later France. That an invasion would be necessary at some point was never disputed, with or without Walt Disney.