How did American foreign policy change between 1920 and 1940?

In 1918, World War I ended and in 1941, World War II began. In between the time was the Roaring 20s era (a time of economic boom) and the Great Depression (quite the opposite). During this time, the US looked inward to focus economic growth (during the 20s) and smooth out the depression with the New Deal (in the 30s). The US adopted an "isolationist" policy in which they pretty much ignored (for the most part) foreign affairs. They didn't not want to nor did they need to get involved in world politics and warfare until 1941. You know what happened afterward.

there was no economic boom at all. when the war ended unemployment jumped to over 11%. farming dropped off because there was no more foreign demand for American agriculture. America always had said that they wouldn't get into foreign affairs but as history shows they always have.