Well in the current state of the world it is highly unlikely that anyone would be able to risk/ even drag in enough countries to make it a world war, if there is some dramatic change in world politics then there is no way to predict who will be against who
Once we (america) dropped the first nuclear bombs we were on top of the food chain. But now that pretty much every world power has them if one country drops a nuke of two, the rest will soon follow. I see no need to even debate this because we are still fighting a war in Afghanistan.
China: Give us money, noa!!! US: *troll face* Someday, someday...we are too busy wasting our money.
China: Fine be that way!
Next thing you know, war. Will it be that way? Probably not in the close future or if the US actually do pay their debt. Will it even be a WW3? Who knows? Hopefully it won't happen.
WW3 would probably be the worst war in the history of the world if it even happens. Also it would probably start land and its minirals. I mean some countries are in so much debt they have put themselves for sale. (I hope I am right about the sale part)
I'm sure that the main forces would be America vs. North Korea. Only thing is, North Korea hates almost everybody except themselves (their motto to the world almost literally translates to "go f*** yourself", so I'm not sure who else would be on their side to back them up. Although, if America goes into debt that is so bad, we might start the war (but make it look like the North Koreans did, of course) to suck up the economic benefits (we lifted ourselves from the Great Depression when we went into WWII).
I'm sure that the main forces would be America vs. North Korea. Only thing is, North Korea hates almost everybody except themselves (their motto to the world almost literally translates to "go f*** yourself", so I'm not sure who else would be on their side to back them up. Although, if America goes into debt that is so bad, we might start the war (but make it look like the North Koreans did, of course) to suck up the economic benefits (we lifted ourselves from the Great Depression when we went into WWII).
American governments have been very very stupid in the past, and although the NK's look mental I willing to bet neither is so mad or stupid as to risk a war, since they bothe have nuclear weapons.