Anotherday,
If you are talking about South Korea, then yes, I think it's a fair possibility that Vietnam would now resemble South Korea. The people could have been spared unspeakable horrors and South Vietnam was on the cusp of being democratic, free, prosperous and safe. But, the treachery of many in US politics (Democrats in the 94th Congress) scuttled that dream.
Five minutes watching PragerU is time well spent.
The truth about the Vietnam War
"Did the United States win or lose the Vietnam War? We are taught that it was a resounding loss for America, one that proves that intervening in the affairs of other nations is usually misguided. The truth is that our military won the war, but our politicians lost it. The Communists in North Vietnam actually signed a peace treaty, effectively surrendering. But the U.S. Congress didn't hold up its end of the bargain. In just five minutes, learn the truth about who really lost the Vietnam War."