Ok. Not considering the sheer absurdity of this ethnocentric perspective taken to this level, what, considering there are dozens of other Western liberal democracies around and the UN, gives the United States the right to decide which foreign governements should be toppled or not?
Also, you're only considering Human Rights violations against one's own population, right? Otherwise I'd be anxious to see you suggesting Washington should have invaded Israel after white phosphorous was used against civilians in 2009, or after the Sabra and Shatila massacres, in 1982, or, instead, defending the widespread use of Agent Orange by American forces in Vietnam as morally justifiable.
Lastly, do you consider racial segregation a serious Human Rights violation? If not, I'd be delighted to know why. If you do, however, I'm interested in knowing why you think a country which supported the South African apartheid regime until its last breath should be the moral judge. Alternatively, wouldn't American racial segregation until the 60s be, by your own logic, cause enough to justify a foreign intervention in the US?