Isolationism is great in theory but when the U.S. tries to practice it we get involved in involved in wars anyway.
Something I found:
American Isolationism
Isolationism
When America joined the Great War in 1917, it tilted the balance against the Central Powers (Germany and her allies), because of her large population and industrial might. When the war ended, President Wilson was in a strong position to influence the peace treaties -the peace settlement was based in fact upon his "Fourteen Points", e.g. a new international body called the League of Nations was to be set up to keep the peace between nations.
Sadly the Americans turned their backs on Wilson (he lost the 1920 election) and on Europe. Many Americans believed that the sacrifices they had made in the Great War had been a waste of money and men. They were opposed to anything that might drag America into another European war. So the USA did not ratify the Treaty of Versailles (officially accept it), nor did she join the League of Nations or the International Court of Justice. Many Americans simply wanted to enjoy the prosperity that had developed in the previous decade and felt that foreign entanglements would threaten it.
During the 1920's and 1930's, America was in isolation, i.e. she kept I herself to herself and took little part in international relations I (conferences and treaties between the nations) .In addition America, isolated herself in terms of trade. Tariffs (import duties) were put on foreign goods to protect American industry. (Because they could not sell their goods to America, European countries could not afford to buy agricultural goods (farm produce) from the USA. This was one of the causes of the Depression.)
America turned its back on Europe in another way. It cut down the number of immigrants allowed into the USA. America was a nation of immigrants. (The native peoples being the dwindling number of Indians, who were largely restricted to remote reservations.) Up until the Great War millions of people, mainly from Europe, had gone to America to seek their fortune and/or escape poverty and persecution. British people, especially the Irish, Germans and Jews, particularly
from Russia, were amongst the largest groups. In 1921 the "open door" policy ended and quotas (a fixed number each year) were introduced. By 1929 only 150,000 immigrants per year were allowed. What was especially unfair was that the system favoured W.A.S.P.s (White Anglo-Saxon Protestants) from northern Europe. The people who were most desperate to get to America, e.g. the poor of Italy and Greece and Adriatics found it difficult to get visas (formal entry documents).