There isn't a chance in hell Russia and China end their entire existence just to defend a war against North Korea that the North also happened to start.
How do I know that? Tons of historical evidence says it would never happen. Vietnam, Cuba, Afghanistan, Iraq, Iran, the original Korean War. There have been countless proxy skirmishes over the decades. None of the majors are even remotely interested in committing suicide for a proxy.
We invaded Korea with hundreds of thousands of troops, and fought a real war with massive casualties. We even fought a war with China at that time. Nobody launched any nukes at the US. Nobody is going to launch nukes at the US in the parent scenario either.
This isn't a video game. You launch nukes, everyone dies, and your civilization and culture is erased for all time. Russia would see a thousand nukes rain down on it, obliterating every relevant city. Ditto China. North Korea is not even remotely worth it, and they know it.
You're right about Korea being a limited war. Both sides had protected rear areas that were vital to the war, and were careful not to step over the line.
However the USSR had only tested their first a-bomb in 1949, and their strategic delivery systems were .. minimal .. for years after that.
A simple visit to his website, and wikipedia page, convinces me that Joel Skousen is about as non-authoritative a source as one can possibly get on this subject.
> Then there is a nuclear strike on the US from Russia and China in retaliation
This is a huge jump in logic without any explanation.
Classic Mormon survivalist subculture crazytalk.
If those countries wanted to commit nuclear suicide, they could have and would have done it a long time ago. The past had a lot more provocations that could have been used to justify it, than the recent times have.
If China and Russia launch against the US, we know it in seconds and launch against both them. Which means that within an hour, China Russia and the US are basically no longer major international players.
They know it's suicide. They know we can respond and do as much or more damage. They won't do it, neither will we.