You are correct to ask the questions it would be a few more articles to give you a good enough answers

Russia is ruining out of men that can fight the attrition wars of its past because of there low birth rates

If the war last for another 5 years as the Russians keep fighting the why they are the Ukrainians would be dealing with USA problem in regard to

Russa

As for China they are going to have big proplems with there demographic decline but if China went to war to day the USA could to starve the country for 6 months by blocking trade to China in the

Indian sea