How did U.S foreign and domestic policies change during World War II?
They changed as the USA entered the war.
American and domestic foreign policy during World War 2 were linked in that once America entered the war it had a significant impact on its economy.
When we say during World War 2 we must remember that the USA did not enter the war until December 1941 after the attack on Pearl Harbour. Even then there was no guarantee that they would become involved in a war in Europe. It was Hitler who declared war on the USA.
Prior to that American domestic politics were dominated by the arguments between interventionism and isolationism. President Roosevelt had to tread a fine path in providing limited support to the UK whilst being careful not to turn public opinion even more against involvement in a war thousands of miles away.
Japan's failure to deliver a knockout blow at Pearl Harbour meant that the US economy, on a war footing, was powerful enough to produce military hardware on a scale not seen before which would lead to victory in 1945 and the USA emerging as the most powerful country in the world.