It's a giant mess. I don't think Pot would have gained the support/power that he did without the US indiscriminate bombing. Much like the creation of ISIS and the strengthening of the Taliban in Afghanistan, it turns out people don't like the people dropping bombs on them. They'll turn to whoever is fighting the bombers.
The US involvement in Vietnam would have already been over before the uprising of Pot had Nixon and Kissinger not skuttled peace talks to help Nixon get elected.
It’s not like Cambodia was a stable democracy before the bombings.
The Khmer Rouge and other opposition groups were fighting the government in an armed conflict since 1950. The Khmer Rouge controlled almost half of Cambodia’s territory 10 years before the bombing.
In the grand scheme of Cambodias civil war, the US bombing didn’t play that big a role at all.
The US involvement in Vietnam would have already been over before the uprising of Pot had Nixon and Kissinger not skuttled peace talks to help Nixon get elected.