Is there a
world war today or not - I would leave this to future historians to debate.
Just a few thoughts at the moment.
1. World wars of the last century caused so much pain to such a large part of humanity that post WW2 public mentality suffered from the very thought of possibility of WW3. Especially, when such thought was connected to the "unavoidable nuclear Armaggedon" - and still is.
2. The more I learn about WW2, the more I think about it as not a "war" but about a "conglomerate of wars" (sorry, I can't find a better English definition). Different countries with different objectives. Objectives that changed over time. Aggressions on different scales, global and regional. Civil wars - something that is often overlooked. Even the period of WW2 1939-1945 became questionable when you look deeper into the Second Sino-Japanese War.
3. Regarding the "overwhelming effort towards a single aim" and the "single endgame" (I borrow from
nuuumannn
), I like the definitions and the logic behind them. At the very least, they help to think about the world wars structurally.
4. Saying that.. I would argue that the single aim didn't appear at least not publicly, until the Casablanca Conference in 1943. Even then it was yet to be agreed with the USSR and China.
Talking just about the Big Four, was the ultimate surrender of all Axis a single aim for every one of the Four and at every moment of WW2, even in 1943-1945? How much Chiang was interested in the destruction of Germany (apart from the hope of getting a larger share of Allied material support)? What about countries that joined the Allies at the last moment as Turkey or those who changed sides? Or nations such as India with a population larger than all Allies China excluding, where Bengali famine and Partition are much more important than wars in Europe and the Pacific and where Subhas Chandra Bose is a national hero? Did the aims of the USSR and Polish Government coincide through WW2? Etc.