It’s really not debatable at this point, the US at the very least did support Pol Pot and his rise for power, although most of it seems unintentional. Bombing campaigns heavily damaged Cambodia, if it were infrastructure, the economy and its upwards of 50,000 dead. This would serve as motivation for the increasingly popular Pol Pot who would later assume leadership in the newly formed Democratic Kampuchea from 1975 to 1979.
However, did the US INTENTIONALLY support The Khmer Rogue, Democratic Kampuchea and mostly importantly Pol Pot, who they saw as anti-Vietnamese and anti-USSR?
Short answer is no. As you said there are historians which trace the rise to power of the regime alongside the failed US interventions in Indochina but the US did not support the Communist Party of Kampuchea nor the state of Democratic Kampuchea. DK's friendly countries were not in 'the west'.
The S.S Mayaguez incident in the wake of the CPK taking over Cambodia would make less sense too if they were supported by the US. Similarly, the pages upon pages of 'confessions' elicited in a torture facility like S-21, with the accused frequently being goaded into explaining their connections to spy networks of the CIA would also be hard to make sense of if the regime was being backed by the US.
The picture certainly changes after the regime fell, and the Cold War realpolitik kicks into gear. For more on that feel free to read this answer about the US and British support of the KR