The Korean War, which was between North Korea and South Korea. The United States were on the side of the South Koreans.
About 50 nations fought in WW2 but basically the whole world was involved.
The US had slowly become involved with WWII through Roosevelt's Lend Lease program, providing supplies to the British as they fought the Germans, but the defining event that fully committed the US to the war effort was the Japanese bombing of Pearl Harbor.
It changed the way people fought, and the nations who could create the best swords became more powerful.
The three main nations that fought against Israel in 1967 were; Egypt, Syria, and Jordan.
The Vietnam War, technically, began long before France or the US became involved. The early motivations were due to religious and political disagreements. In the 1960's and 70's the Allied nations fought in Vietnam to stop the spread of communism.
Both sides fought for the neutral nations hoping to gain more allies. The neutral nations, by definition, did not fight
It is because, even though they were very far, were at alliance with the Commonwealth (Britain) and had fought with them.
Woodrow Wilson played a huge role in determining if and when America would get involved in World War I. He also fought for the League of Nations to help avert another World War which won him the 1919 Nobel Peace Prize.
The key nations involved in the fighting were the United States, the Soviet Union, Great Britain, Germany, Japan, and Italy. Nations including Poland and France fought in the war but were overrun. The war raged across several other nations.
The United States aligned themselves with the United Nations. It also became over involved with the Cold War. The US fought in Korea and the Viet Nam war in response to the Cold War. There were other small skirmishes until the Gulf War and Gulf War 2.
The war was fought primarily (though not exclusively) in Germany and at various points involved most of the countries of Europe. Naval warfare also reached overseas and shaped the colonial formation of future nations.
Australia fought in wars with Britain because Britain OWNED Australia until after World War 2. The wars after that in which they fought together with the Brits were when they were doing United Nations military functions. They have not fought in any war because OF their desire to support Britain but because they are allies together in the United Nations.