Yeah, but... the quoted phrase should not be taken literally as a statement about battlefield capability.

It was a political struggle for legitimacy, not just territory, and the enemy did not have to win any battles, just avoid losing until the political will collapsed.

The thing is, military power does not automatically translate to political success, and guerrilla fighters do not need to defeat tanks and jets, they just need to survive, persist, undermine legitimacy, and exhaust the opponent's political will.

So, in this sense, the US was not beaten by farmers, it was beaten by a strategy that made military superiority irrelevant.