It seems improbable given the family's wealth and political power in the United States (so they have a clear vested interest in preserving America and capitalism), but why else would there be a secret Chinese bunker under Calvert Mansion? I find it hard to imagine that Chinese agents built it in the mansion's grounds without anyone noticing.
Seems pretty reasonable.
Mebbe it's got a correlation to real life: The CIA has performed many simulations of a possible WW3 scenario and in the vast majority of them, the Chinese come to the top victorious.
Perhaps the Calvert family saw more value in remaining at the top of the political food chain, regardless of who that meant siding with. Approaching, or approached by, the Chinese they strike a deal to spy on America, or to support Chinese spies in America for a promise of safety after a possible Chinese victory in the Resource Wars.