China was valuable because it's currency is easily manipulated.

SA was valuable to them because they were the key to maintaining the petrodollar.

Russia's role in the eventual collapse of the US dollar is less obvious but they have a HUGE interest in seeing the end of the petrodollar.

China is the largest state holder of foreign US debt, which could give them tremendous leverage someday.

China is a threat to the US in many ways but they were the key collapsing our economy. In retrospect it always seemed odd that the UK didn't protest the loss of Hong Kong more than it did but that was a strategic "loss" since it just gave them more direct control within China.