The biggest killer of Chinese in the 19th and 20th century were....other Chinese, not to mention other Asians. I'm not sure why America is singled out when war just happens to be brutal. The PLA has been especially brutal in its treatment of their countrymen (e.g. The siege of Changchun).
Likewise, the north Vietnamese really practiced total war to an extreme, and well, it worked out for them at high costs they were will to pay.
No that's stupid and not even thorough. Did Australia have a genocide campaign in Asia? We were involved in all the same wars. Of course in terms of sheer body count we probably killed more Turks then any other single nationality in the 20th century. But that's my guesstimate based on Gallipoli being a large campaign for us, and in turn brings us back to just how useless and stupid this type of reductionist historical metric is.
Semi-related, our (Australian) hands aren't clean of genocide either: https://en.wikipedia.org/wiki/Black_War is often considered genocide, though there is some debate on the matter.
> I'm not sure why America is singled out when war just happens to be brutal.
Though I agree with the US hardly being "the" aggressor in the world, the second part, that "war happens to be brutal", is precisely the reason starting one was declared the worst crime of all, encompassing all other crimes. You can't just say "oh well, it's war after all".
Likewise, the north Vietnamese really practiced total war to an extreme, and well, it worked out for them at high costs they were will to pay.