Retain the guns on the jets; air to air combat (dog-fighting) was alive and well.
The retention of guns on jets.
We won.
How the Communist Party is dragging down the good Vietnamese people.
The only big lesson learned was North Vietnam was not invaded. During the Korean War, N. Korea was invaded; that brought in Red China. That strategy was not repeated in the Viet War.
The same lessons were learned as was learned in America, only on a lesser scale, which was relative to Australia's population and troop levels.
The lesson learned was "look before you jump."
They did what they always did after fighting a war (in the 20th century); trained for the next one (often studying lessons learned from the past war).
The only realistic lesson was super-sonic jet warfare. The US hadn't before Vietnam, nor after Vietnam ever fought a modern hi-tech airwar against a determined foe equipped with the latest in AAA, SAM, Radar, and MiG aircraft. The key word here is "determined."
The the United States needed to go to an all volunteer fighting force because the draft was not productive in many standpoints.
Korean War & Cuban Missile Crisis. Both brought the issue of atomic weapons to the fore front. Vietnam didn't, because the lessons learned from those two experiences were applied to Vietnam...(that's why North Vietnam wasn't invaded).
Lessons learned from a lost war are often more valuable than lessons learned from a "won" war. Constant victories (won wars), as the US has consistently experienced, caused "victory disease" and "complacency." The lessons learned from Vietnam went directly into "Operation Desert Storm (January & February 1991)" (both Desert Storm US General's, Schwarzkopf and Powell, were Vietnam Veterans/Americal Division). Desert Storm resulted in the quickest, most surgically clean (precise), one sided victory, with the least amount of US casualties in US history; 100 hours of combat, and less than 200 fatalities.
For the typical citizen at large: 1. An all volunteer military (no more fear of being inducted into the service). 2. Voting age lowered to age 18 (used to be 21). For the military population: 1. The F22 Raptor still has guns on it thanks to the Vietnam War. 2. All armies now use the assault rifle (pioneered in the Vietnam War). 3. The M1 Abrams MBT (Main Battle Tank) was pioneered on the combat experience obtained from the M48 Patton's combat experience in Vietnam, among other conflicts. 4. Today's Kevlar helmet is based upon lessons learned in Vietnam combat. 5. Today's Blackhawk helicopter is based upon lessons learned from the UH-1 Hueys (Iroquois) combat experience in Vietnam. Today's AH-64 Apache helicopter gunship is a direct descendant of the Vietnam AH-1 Cobra attack chopper. 6. The A-10 Warthog took some of it's design lessons from the A1 Skyraider's (code named Sandy and Spad) experience in the Vietnam War. 7. Today's USN riverine forces took their ideas directly from the USNs "Brown Water Navys" riverine forces in Vietnam. Just a few examples.