Mutually assured destruction: Americans are slaves of the US president X, and the Chinese are slaves of the Chinese president Y.
Y would love to extend his dominion and grab X’s slaves, but X threatens to wipe out Y’s slaves for such an attempt. Y is deterred. And vice versa.
Peace is assured, and the property rights of both X and Y are secure, because armed slave owners are polite slave owners.
In addition, though it is hardly important, the slaves are content.