I agree with you about the American deficiencies.
I'm sure you appreciate, though, that the death tolls you gave are skewed. The vastly higher modern numbers are due not to the greater evil of liberalism but to the invention of modern weaponry. Granted, the numbers become hypothetical, but the question would be how many more people the kings of old would have killed had they possessed rifles.
There seems to me an implicit contradiction in what you're saying, too. On the one hand, you say that slavery, war, patriarchy, and oppression were the norms all over the ancient world. And of course I agree with that assessment.
But on the other hand, you say, "Change is a steady state in life, politics, and the world." Assuming you're not talking about trivial or negligible changes, but about progressive ones, I fail to see how you can reconcile that moderate conservative hope with the above, sad observation of the stagnancy of ancient brutality. Almost all of those ancient states were monarchies or other pyramidal power structures which the modern conservative implicitly reveres (given the effect of her principles and policies, as I've argued elsewhere).
So the universality of those ills in the ancient world speaks to the absence of natural progress. Social progress is artificial, not natural or divinely guided or imposed.
You say slavery was ended mainly because of material progress. But that progress was preceded by the intellectual kind, by Protestant individualism, the Renaissance, the Scientific Revolution, and the Enlightenment. So it's doubtful a main cause could be so easily disentangled. Certainly, the philosophical progress entails the wrongness of slavery.