After World War I the US attempted to become less involved in world affairs.
The US refused to join the League of Nations. Although President Wilson pushed hard for US membership, opposition in the US Senate was significant. Americans, after learning of the destruction and cost of World War I, did not want the United States to become entangled in another European conflict which could lead to another devastating war. Americans viewed the nations of Europe as conflict prone and likely to become involved in internal and external disputes which could draw in the United States into another war which really had little to do with American interests.
The US closed the doors to immigration during the 1920's. Early on the US had excluded Chinese, Japanese, and other Asians, but later the US began to exclude even Europeans, particularly eastern and southern Europeans.
http://www.andycrown.net/isolation.htm
The US refused to join the League of Nations. Although President Wilson pushed hard for US membership, opposition in the US Senate was significant. Americans, after learning of the destruction and cost of World War I, did not want the United States to become entangled in another European conflict which could lead to another devastating war. Americans viewed the nations of Europe as conflict prone and likely to become involved in internal and external disputes which could draw in the United States into another war which really had little to do with American interests.
The US closed the doors to immigration during the 1920's. Early on the US had excluded Chinese, Japanese, and other Asians, but later the US began to exclude even Europeans, particularly eastern and southern Europeans.
http://www.andycrown.net/isolation.htm