The US dollar is useful to countries like china is because the US government acts as a debtor of last resort, allowing them to park surpluses in treasuries.
Which ultimately derives from our mammoth consumption. If Chinese consumption eclipses America's and their economy rebalances, they will have lots of Chinese consumers buying goods with renmimbi, leaving sellers offshore with boatloads of the currency to find investments for. (I consider this to be a moderate risk, and not one which would supplant the U.S. dollar but instead cause it to share the world stage.)
TL; DR Bitcoin is not a serious threat to the U.S. dollar. It promises huge profits to banks, which is why they're salivating over it.
The Chinese government is not interested in filling this same role, even if now anemic Chinese consumption somehow picks up, they will probably still want to maintain absolute control over the exchange rate.
https://datahelpdesk.worldbank.org/knowledgebase/articles/11...
To the extent there is a legitimate threat to dollar supremacy, it is in the Chinese renminbi. The U.S. dollar is ascendant because of the huge base of American consumers, who buy stuff with dollars others then need to find investment for. Plain and simple network effects.