What happened shortly after the United States North Vietnam signed a peace accord providing for the withdrawal of troops from Vietnam?

North Vietnam invaded the south, killed a bunch of people who fought South Vietnam's Army along side with the americans. One of US most worthless political decisions. We did the same thing in Afganistan in the 1980's when the US funded the Afgan Army to fight the Soviets. They won the war and US left them with no resources to build hospitals, schools and other stuff. Wonder why other countries no longer see us as the savior of the free world. We gave into the "peace at any price freaks" and cost the lives of thousands around the world. Same in Somalia