That is not the US policy. The US policy is to use the threat of overwhelming force, nuclear and non-nuclear, for leverage in interstate conflict whatever that

That is not the US policy. The US policy is to use the threat of overwhelming force, nuclear and non-nuclear, for leverage in interstate conflict whatever that conflict may be and whether or not that conflict is a threat to the United States or its persons or just the outcomes it is interested in. It's possible that nuclear forces could be used in a scenario like you suggest, but to round that up to policy is inaccurate and it is misleading.