You don't seem to have an understanding of basic strategy. China will probably use this opportunity to take back Taiwan. And North Korea might as well invade South Korea while we're at it.
There is the potential for great misery and destruction from NK, but that's mostly due to the fact that a lot of well off urban areas are within NK artillery range.
I'm not so sure about Taiwan, either. Ukraine is right on the border of Russia, no shipping, no mountainous terrain, and no direct treaties with the US. China has already said in the event of a shooting war they'd consider US allies as legitimate targets, so a Taiwanese war means Japan, Australia, SK, and maybe NATO entering the fray. It would be an ugly, mountainous fight, possibly leading to a guerilla war / insurgency.
In 20 years after technology (chips, etc.) transfer back to the US there isn't really any reason for the US to give a shit. Why risk Ukraine-ing yourself when you can just let economic and demographic forces do it for you?
Why take back Taiwan when they can take back parts of Russia that Russia previously annexed?