The US isn’t the world’s most vicious government because it happens to be the most powerful, it’s the most powerful government because it’s the most vicious. It’s the power structure which was willing to do whatever it takes to rule the world, no matter how profoundly evil.
Genocides. Starvation sanctions. Nuclear brinkmanship. Imperialist extraction. The deliberate creation of failed states and humanitarian catastrophes. Policies designed to keep entire regions in a continuous state of division and strife. The United States and the globe-spanning empire structured around it have inflicted depravities upon our species which cry out to the heavens for vengeance. If you could truly comprehend the scale of the suffering it has created over the years, even for a second, you would never stop screaming.