Exactly. And if the US had kept it’s word to it’s South Vietnamese ally, kept them logistically supplied, and provided the same level of air support that blunted the North Viet’s 1972 Easter Offensive, then the later offensive would probably have resulted in failure also.
South Vietnamese ground units, particularly their M-48a3 tank units, did some very determined and resolute fighting, particularly on the DMZ and the II and III Corp tactical zones.
The word “If” is the biggest little word in the world. If we had Operation Linebacker and Linebacker II in 1965 there would’ve been a completely different outcome.