After trying many military strategies and working very hard to broker a peace agreement, the United States eventually gave up on the Vietnam War and left the country, allowing it to be taken over by the Viet Cong in 1975.
The Vietnam war was important for a number of reasons. First, it showed the pitfalls of trying to win a war in a far away nation even with a huge preponderance of money and weaponry: people who live in a country have a vested interest in defending it, a more intimate knowledge of it, and in the end are willing to sacrifice much more to win control of it than soldiers coming in from far away.
More importantly, this was the first war the US ever lost in its 200 year history to that point. The defeat, coupled with widespread knowledge of the leadership incompetence that cost American lives and the atrocities perpetrated by frustrated US soldiers, hurt perceptions of the US abroad and its self image at home.
The war was highly divisive, the first war the US government was not able to get backed by the majority of the population. Prominent newscaster Walter Cronkite spoke out against it in 1968. Students who did not want to be drafted to fight a far off war that was being mishandled took to the streets in protest. The domestic situation at home became highly volatile, and US society polarized in ways that have never been resolved and continue to play out fifty years later.
The immediate result of the Vietnam War was that North and South Vietnam were merged into one country under communist control. In an effort to rid the newly united country of anti-revolutionary ideas, many thousands of South Vietnamese were sent to reeducation camps. Many also fled as refugees.
The devastation of the war itself on the Vietnamese population was significant. Millions of Vietnamese soldiers and civilians had been killed. This made it difficult to rebuild the nation's economy and led to poverty and starvation in the years after the war. It became difficult for post-war Vietnam to receive much-needed international aid due to the United Nation's repeated blocking of the country's official recognition.
The defeat of American forces also led to a reckoning in the United States. The policy of anticommunist intervention laid out in the Truman Doctrine came under question, and the country became much more reluctant to get involved in military actions for quite some time afterward. Many Americans also developed a more cynical view of a government that would conscript young American men to fight in a war that they believed to be unjust.
The billions of dollars spent on the conflict led to a massive federal budget deficit. To this day, the federal government continues to pay billions of dollars a year to many veterans and their families.
The outcome of the Vietnam War was humiliation for the United States. America had originally entered the war to prevent the Communist North Vietnamese and their guerrilla allies in the South from taking over the whole country. Despite the vast expenditure of blood and treasure, that aim was never realized. And so a war that had cost the lives of over 58,000 American servicemen and around 600,000 Vietnamese, Cambodian, and Laotian civilians had ultimately been for nothing. The Communists had won, and proceeded to establish a one-party dictatorship, which still persists to this day.
The significance of the Vietnam debacle was that it showed the limits of military power as a means of halting the spread of Communism. Then as now, the United States had the largest and most technologically-advanced armed forces in the world and yet was still unable to defeat a leftist insurgency highly trained in the art of guerrilla warfare. From now on, the United States would have to be more flexible in its methods of conducting the Cold War, avoiding direct armed intervention where possible and relying on proxies to do its bidding.
On the domestic front, the Vietnam War and its aftermath had a damaging effect on the nation's self-confidence, prompting an unprecedented bout of national soul-searching. To many, it seemed that an era of American greatness was at an end, and that the United States, despite its enormous wealth and military power, was no longer able to impose itself upon the world as it once had.
The final outcome of the Vietnam War was that North and South Vietnam were united under the Communist North in 1975 despite the best efforts of American servicemen who left the area following the Treaty of Paris in 1973. The Vietnam War was important politically because it demonstrated that America would fight against Communist aggression. However, it also proved that American traditional warfare was not prepared to fight against insurgencies and no matter how many bombs were dropped and how much herbicide was deployed in North Vietnam, America could not win against a determined enemy fighting on his own native soil. The Vietnam War also helped to further destabilize governments in Laos and Cambodia and led to one of the largest genocides the world has ever witnessed. The aftermath of the Vietnam War also created a refugee crisis as people who supported the South Vietnamese government left to get away from North Vietnamese attack.
Domestically, Vietnam was important because it created a rift between people and government as the White House told the American people that the Communists were losing but the Tet Offensive of 1968 proved otherwise. The Vietnam War also led to the 26th Amendment giving 18-year-olds the right to vote in elections--this was important as this same group of young people was also being called upon to be drafted into the war. After Vietnam, American military forces are now volunteers, though young men still have to register for the draft. America was hesitant to send more troops into harm's way, and there are some that still use "Vietnam" as a synonym for military quagmire.