Cao Cao could betray anyone but none could betray him. US can betray and accuse anyone and any country in the world but none could do so to revenge. Since the end of the World War II, US has bombed, toppled, and removed many leaders and changed the regime over 30 countries. The Number One Global Superpower has betrayed most of its both allies and enemies. To do so, US has reasoned that it has the obligation to protect human right, protect democracy, depose the aggressor, and uphold the international law.
US and Cao Cao have shared the idea of supremacy or hegemony. Cao Cao wanted to unify the whole empire while US wishes to put the world under its system and values. Contrarily, Cao Cao showed his aggressive ways rather than principles while US does so in the name of principles.
US uses the International Law in three objectives: 1. To promote the democracy, peace and stability, 2. To gain its legitimacy to fight against its opponents, and 3. To To expand its power and influence further as far as possible.
Cao Cao imprisoned the king in his capital to gain his legitimacy to accuse and fight his opponents whereas US uses international law to claim its rights to do what it wishes.