So, I'm writing a sci-fi novel that takes place roughly 200 years or so in the future. I'm currently creating a timeline to figure out what nations would be space-faring nations and which ones would be in bad shape. I know that I want the U.S. to break up into five different countries and I want China and Russia to be competing in the next space race. While I was figuring out what was going on with the rest of the world, specifically the countries on the Korean peninsula. I keep going back and forth in my head on whether or not I want to have North Korea just collapse and be taken over somewhat peacefully by South Korea or if I want it to be a bit more violent.
I have read a bunch of stuff that tells me if either side were to do anything that seemed threatening the other side would immediately wipe Pyongyang and Seoul off the face of the planet and hundreds of thousands of people would die. But, in every single one, the person always brings up how the U.S. Russia and China would all join the conflict and it would set off world war 3.
What I want to know is aside from massive amounts of casualties in North and South Korea theoretically how might this conflict as well as the rest of the world be affected if the U.S., Russia, and China were unable to join the conflict? I know that a space race wouldn't keep Russia and China from acting but let's just say for argument's sake that it does.
EDIT: rereading my question I realize I left out some information. That's what I get for writing it at 3am. The book will take place 200 years from now but I was planning on the Korean conflict being somewhere between 50-80 years from now. The US will be unavailable to help because at that point they've been going through economic and political upheaval which will lead to it falling and five separate nation's forming amidst the ruins. Both China and Russia are competing to be the first one to 'conqur' space though I know this would not prevent them from taking action if SK invaded NK. In my book I'll probably have it so China invades shortly after SK wins the conflict this will then cause China and Russia to start fighting one another in an actual war instead of the pseudo one they were having over space.
I was wanting to remove them from the equation because everything I have read has included their involvement and was merely curious as to how things might play out if they weren't involved. Specifically I was wondering which countries might support NK as I am unaware of any except Russia and China doing so at present. Does this clearify a few things?