The signing of Treaty of Versailles ended WW1 and the allied powers won. Countries apart of the allied powers were UK,France,U.S
The US did not join the League of Nations and stayed isolated to avoid all future conflict.
U.S, Great Britain, and Japan signed the Four Power Treaty for not expanding territory.
Between 1880 and 1920, 25 million+ immigrants came to America. After WW1 the need for unskilled labor went down.
The U.S put up tariffs and became pacifists
To prevent another World War, but it had little effect in stopping the rising militarism of the 1930s or preventing World War II. 1917, the U.S. began to extend cash and supplies to its European allies, expending more than $7 billion in government funds by the time of the armstice in November 1918.