All societies are genocidal, but America is exceptional because of the art and technology it contributed to the genocide effort.

really simple paradigm shift:

ask why they downplay their atrocities in some contexts but brag about them in others

IE: all over reddit, or anywhere Americans congregate, has a slew of comments like "Iran's about to find out why we don't have free healthcare" and the like, which are obviously prideful/bragging

The reason they do this is that there are two paradigms--a power and a fairness paradigm--the former prides itself on brutality/killing while the latter on equality/kindness

All the comments you see on reddit are americans getting drunk off power paradigm in order to feel a vicarious sense of self-esteem

The problem is that power depends on implicit consent of the less powerful to be governed. And if things are too inequal for them, they will fight back, and the whole system will become unstable and less powerful. This is why liberals fake niceness towards POC, it's also why Russia/China/etc are allied, etc.

Comments like OP are just trying to have their cake and eat it too. They will never shut up about "positives" (american inventions/culture) but when confronted about negatives (genocides and war killings) , they always say "uh uh but wait, every people committed genocide at some point in history". Imagine if whenever someone was talking about Galileo or something, I said "uhh but actually India invented numbers and China invented gunpowder". You would say I was being insecure and defensive, and you'd be right if I did that EVERY TIME that happened, and this is also exactly equivalent to what every American does when there's a discussion about American genocides and war crimes--they respond with extreme defensiveness because the reality is that yes, China and India were behind for the last few hundred years, and America/Europe did commit the biggest genocides of the last 500 years.

This deflection is an attempt to save face during value inversion--when the values are inverted into fairness morality, and violence/brutality are now bad, suddenly America becomes unexceptional and just a footnote compared to every other human empire that existed. When we're back on reddit however, "Vietnam barely even won, look at our K/D ratio"