It's not that simple, though. A lot of people - a
lot of people - have no idea that during the "Dark Ages", huge swaths of the rest of the world (larger than Western Europe) were going through a Golden Age. It took me rather a while to realize that myself.
And, since WWI was fought in large part over colonial resources and Japan was involved, and since Japan was a major power in WWII (and China was involved as well, if only as Japan's victim), I'm pretty satisfied with "World War" as descriptors.