I doubt that using bitcoin the Chinese can destroy the US economy for the following reasons:
The largest reserves of oil worldwide possess Saudi Arabia and Venezuela. The first country has friendly relations with USA and second one there is no way to escape from American's influence. The third country is Canada.
Secondly, the American's military presence is global. China is trying but so far has not succeed more than its borders.
Finally, China has many factories but the expertise derived from?
It is the last straw that broke the camel's back
The Chinese may not actually want to destroy the US economy to dust and ashes since that would backfire on themselves as you yourself say. They just want to become a new overlord on the block and rule the world just like the Americans have been doing since the collapse of the Soviet Union. Also, don't forget the other aim, i.e. rendering Bitcoin itself useless. Apart from that, we don't really know how friendly the relations of Saudi Arabia with the US will be in the nearest future now when Trump has become a new POTUS. In any case, today the US has enough of their own oil, so Saudi Arabia is irrelevant and thus can be punished with a vengeance and no one would give a fuck about them
