Chineese have lots of money and most of it has been borrowed by US. Now if the realtionship gets worse or US goes bust who loses the money?
Not that simple.
external debt can't be unilaterally abrogated by the debtor, unless the states got rebuilt after subversion. ref: law of nations (India had abrogated some of its external debts in 1947 when declaring independence.)
External debt is a money you've used on loan, debt relief doesn't bring any instant economic advantage, but promises a sprightly future. while creditors like China doesn't live on lending, hence no fear for a consequent breakdown.
Instead, capital withdraw might be the worst aftereffect in condition of war, but the 1.3 tril foreign-exchange reserves is a fund inflow to China, if war makes unreasonable efforts.
last but not the least,freezing of assets, US has currently over 85 bln dollar assets in China, 50 times Chinese investment in US.
A research by Chinese national security subject indicates that a local war will cost China's financial system at least 3 to 5 years to digest the negative impact, with reserves loss about 400-500 billion dollars. On the whole, for China a limit war will cause an economic loss equivalent to most of the achievement of a five-year plan.
and a full scale Sino-US war is absolutely unbearable for both countries.