Why has the United States Congress protected Vietnamese Communist Regime?

Why has not the Vietnamese Communist regime trained a few Vietnamese communist leaders like a leader To Hiem Thanh, but the Vietnamese communist party has been training so many communist corruptions to destroy the nation and the Vietnamese people? Certainly, the American Government not only respected the Vietnamese communist regime but also supported the Vietnamese communist government regime. Let it serve as the core national interest of America- Therefore, the United States Congress has self-torn shreds of multilateral and bilateral treaties and the American laws and Constitution with the Republic of Vietnam.