Especially considering that the US began arming the "Khmer Rouge" in 1979, and then began heavily arming them a few years later.
Hilariously the Wikipedia article is titled "Allegations of US support for the Khmer Rouge" even if it describes factual US support (in the UN), and a bunch of "allegations" based on internal reports confirming them.
https://en.wikipedia.org/wiki/Allegations_of_United_States_s...