I think that South Vietnam turns out to be one of the forgotten casualties of the conflict. The raging battle between the North Vietnamese and the American forces ends up making South Vietnam the rope in the proverbial tug of war. In the end, I think it ended up creating an unstable nation as the American forces sought to control the nation over the Communist North. While the intent was to have the Southern forces help the United States, as the war escalated, it became clear that the Southern section of the peninsula was being overtaken by the presence of the American forces. In the end, they were silenced through this escalation. This is sad because it was the fear of being overrun by Communist forces that helped to drive the presence of the Americans. It seems odd that in order to stop silence, the American escalation ended up creating it.
It exposed ordinary and innocent South Vietnamese civilians to violence and war, which was devastating to their society and to families. The war shuffled their population from the countryside to the major cities as refugee populations swelled and the village network was destroyed or relocated. There was massive environmental damage from extensive bombing and spraying of defoliants. Even today, there is a large number of unexploded bombs and mines left in the Vietnamese countryside.
After the war, there was a bloodbath where an estimated 200,000 South Vietnamese were executed by the new communist regime. Hundreds of thousands of others were sent to "re-education camps". And the country was converted to a communist economy where all private property was confiscated.
South Vietnam was the place hardest hit by the war, although the war probably allowed it to exist as a separate country much longer than it would have without the war. Two years after the US got out of the war, the South fell and the country was unified under communist control.
The South was hit hard by the war because almost all of the ground fighting of the war occurred there. This meant that villages were destroyed and people were put in the "strategic hamlets." It meant that the jungles and fields were sprayed with Agent Orange. This killed vegetation and led to birth defects in people. It meant that many people were killed -- both soliders and civilians.
The loss of the war meant that many people had to flee or try to flee the country because they had opposed communism.