It was that whole invasion thing. Against world domination and mass murder.. How would anyone feel not doing so was right?
Also, we had already fought Germany and what was essentially the Axis in WWI, and the alliances from then still held.
allies
The US entered the war in April of 1917 and were on the Allies side.
Allies
allies
South Korea
Allies
The US joined the war on the side of the Allies on April 6, 1917.
Allies (british, French side)
The US fought on the side of the Allies. The other side was called the Axis.
The Allies .
The Allies
allies