You mean the United States? The reason we entered the war was because of the sinking of the Lusitania through the use of unrestricted submarine warfare by the Germans, as well as other U-Boat threats.
Spain's dictator Francisco Franco kept his country out of World War 2 by declaring neutrality.
Britain had a treaty to protect the neutrality of Belgium.
Policy of neutrality/ American neutrality
Declaring a war
neutrality
Switzerland has a long history of neutrality.
American neutrality in the 2nd World War ended because of the attack on Pearl Harbor.
America declaring war on Nazi Germany and joining the Second World War in Europe.
Nostradamus
American neutrality in the 2nd World War ended because of the attack on Pearl Harbor.
The Swiss policy of neutrality provided the allies with some assistance in World War 2
That is called "neutrality". Sometimes the neutrality is respected by the warring countries (Switzerland in World War II) and sometimes it is not (The Netherlands in World War II).