North Vietnam & VC living in South Vietnam (supplied by USSR/Red China) against US/Australia/South Korea/South Vietnam/New Zealand/Thailand/Philippines.
North Vietnam won them.
Two separate countries: South Vietnam was officially called RVN (Republic of South Vietnam). When US servicemen landed in country, they were greeted with "Welcome to the Republic of South Vietnam" (enjoy your stay).
The United States and the Soviet Union were the two countries on opposite sides during the Cold War. The Cold War ended in 1991.
Vietnam was split into two countries during the vietnam war, the north was ruled by Ho Chi Minh and the South by Ngo Diem.
Only one nation won the Viet War; North Vietnam. Interesting question, which two nations did you have in mind?
Laos and Cambodia were both drawn into the Vietnam War because of atrocities the people of these two countries suffered under the hands of North Vietnam. South Vietnam and other countries were trying to keep the North Vietnamese army from spreading Communism in these countries.
North Vietnam and South Vietnam. Also, to name just a few: the USA, China, Russia, South Korea, Australia, France, and England. A great many countries fought in the Vietnam War from 1945 to 1975.
After the war, there was a reunification of Vietnam. So the answer is "One country".
Laos and Cambodia.
Vietnam , America , and Russia
Basically, the Vietnamese sides, north and south, each had allies and supporters. These allies joined with the troops in Vietnam. The US was on the side of the south. They lost.
Alecander Hamilton and Tomas Jefferson