It would be great to have your detailed view of how the IFC PF and Equator Principles apply in US in light of what US is and is not signatory to. Also how well IFC addresses civil rights.

Treaties on human rights include the right to health. we have had legal opinion in the past that this is about progressive realization and that decisions by government that would reduce health are then in breach of treaty obligations.

In HIA I'm usually just constructing a justified argument to a corporation who are concerned about their reputation, social license to operate and investment risk rating. They are usually ahead of the national government in which project is located.
I think the IFC PS anticipates your point and expects clients to act even when government is uninterested. It's a loan condition.