Slavery, while unwise and wrong, was legal at the time, which is the test we are applying here. We are discussing lawlessness versus lawfulness, not your or my personal definition of morality.
What you describe as the spanish-american war of aggression was lawfully declared by our Congress under our constitution and the laws of nations at the time. You fail to explain how it exemplifies systemic disregard of constitution or law, merely that you disagree. BTW, we see this as a war against European colonialism and imperialism.
All the other things you mention, which constitutional principle do they violate?
Congratulations to Finland. But with a population (5.4M) smaller than Missouri (6M), only three ethnic groups (Finn, Swede, and Sami), and a completely different culture from us, its easy to see why you have such a peaceful society. I could pick a small American state with a mostly all-white population, Vermont for instance, and also demonstrate low levels of violence and low infant mortality. I not sure what that proves about respect for the constitution though.