If you go by deaths, USA did very well in Vietnam. However, with wars of insurgency people like The Butcher showed that far more deaths are required to win than is palatable
I was going to respond to each of your points carefully, but since you mentioned that Iraq’s leadership remained in power after 1991 as some kind of rebuttal, I am not certain I should. Indeed, overthrowing Iraq’s government was not a war aim there.
Yes, if war was a game where the victory condition was killing the most people... well, actually, the Khmer Rouge would have won the wars in the region, by a wide margin.
But its not, so “yeah but we killed more people than our immediate enemy” is... irrelevant, mostly. Killing people is a means, not an ends, in war (I mean, except when your war aim is extermination, but that's not the general case.)
> but since you mentioned that Iraq’s leadership remained in power after 1991 as some kind of rebuttal, I am not certain I should. Indeed, overthrowing Iraq’s government was not a war aim there.
I’m not the one that said a unifying feature of the post-WW2 wars was that the US destroyed the pre-existing government and thereby won, when that is very much nor a characteristic of those wars in general, or the specific cited examples originally provided (leaving off Iraq I, it wasn't a feature of Korea, Vietnam, or Afghanistan, specifically cited as examples upthread, either.)
The US isn't conventionally, even in the US. viewed as the victor in Korea (war is still in progress, with a long but imperfectly observed ceasefire), Vietnam (one of the few wars the US generally acknowledges as an unambiguous defeat, thought right wingers will often say that we won “militarily” and lost “politically” or some other cope), or Afghanistan (recently added to the list alongside Vietnam).
Also, the prewar opposing in Korea, Vietnam. Iraq (1991), and Afghanistan did not fall, and in each case remained in power after the war (and in Vietnam and Afghanistan, the primary opposing government ended up in control of more territory as a result of the war, controlling undivided a country which it had controlled only a divided—formally in Vietnam’s case, de facto for the Taliban in Afghanistan—fraction of before the war.)
> With all the post-WW2 wars, we've gone in as a dominant power, as the aggressor
No, we haven't. Not even in a loose sense of “aggressor” in several of them.