I'm sorry, but this is /r/AskHistorians, a subreddit dedicated to questions of the past. Questions regarding possible future scenarios is not accepted here I'm afraid.

However, if I might just leave my own note to this, what made WWI and WWII world wars was the fact that all major powers had colonies which were also brought into play. It was truly a global war in every sense of the word. You had Nigerian soldiers fighting Japanese soldiers in Burma while Brazilian soldiers fought Germans in Italy. The whole world was affected by it in one way or another - even if they didn't understand the reason for why the war was fought in the first place.