what did the u.s. do-while remaining officially neutral-to guide the course of the war?

Answer 1

Between 1939 and December 1941 the USA was divided between supporting the Allies and supporting the Nazis.
While they sold arms and other supplys to Britain and France they were also involved in helping the German war effort.
In 1940 Standard Oil of America gave the Germans the process for making synthetic rubber, a vital war material at a time when they were having difficulty obtaining natural rubber.
This probably prolonged the war by several months.

Answer 2

Which war? If you are talking about WWII we supplied guns, food, ammo and other military items to the United Kingdom and other countries who were our allies during the war. Many of our ships got shot down for doing that too and our submarines. If your not talking about WWII then you have to tell me what war you are referring to.