I completely fail to connect to the narrative of the song. For example Hollywood-forced D-day exaggeration (in the sense of effect on the outcome of war) I can live with. It was a huge thing, not the biggest not the one solely responsible for the outcome, but a huge thing nevertheless.
As for Albion it was never under threat, the situation was shaky because Brits tried to defend their whole empire. Somehow the will of one man being so important for the survival of a country that fields largest Navy and one of the largest armies of the world is a bit moot. The bombings were indeed killing civilians but not on a scale that's too damaging. Britain was somehow defending itself even while having pacific theatre operations so excuse me of not believing this viewpoint.
I don't know the story about morale, public opinion, whether he motivated Brits into fighting, but they had enough to fight with in a first place. Once Japanese stopped being a offensive force (after Midway) Brits were free to regroup their Indian and Pacific navies. After Italy capitulated there was no contender on the Mediterranean.
The war was largely over when Germans failed to induce a strategic blow on Russians and Japanese failed to do the same to Americans. The Allies were larger, more powerful, more numerous. The only way Axis could do anything is force these asymetric theatres because Allies have a less "dense" armies. When that failed, the war was over. There was no going back after Midway as there was no going back after Stalingrad.