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If there is a single most important historical focus for the origins of American ambivalence about Europe, it would be found in the Monroe Doctrine. It is important to note that the Monroe Doctrine does not specifically endorse American isolationism -- far from it -- but it does endorse an American policy of not tolerating European incursions into the Americas. At the time of World War One, the more recent Roosevelt Corollary to the Monroe Doctrine had insisted that America would actually have the right to intervene in the Americas if a Latin American government was somehow engaged in wrongdoing: it is worth noting that in 1916, while America was still declining to enter World War One, President Wilson was engaged in border warfare and a technical invasion of northern Mexico (as a result of Pancho Villa's actions in the Mexican Revolution). This would seem to indicate a strong interventionist strain in American politics, which was borne out when Wilson did ultimately enter World War One. However the larger historical meaning of the Monroe Doctrine indicates an American distaste for European affairs and governments. The isolation held up for so long at the start of World War One presumably because there was no obvious ally that America might support.

Likewise the American population at the time of World War One had an overwhelming number of immigrants, many of whom had come from the now-belligerent nations. There were greater complications as well -- considering America's large Irish population, and the centrality of Irish-Americans to urban machine politics, we must recall that Ireland would go into open revolution against Great Britain at Easter 1916, while World War One was ongoing. Thus the notion of American "special relationship" support for the U.K. was far from obvious -- particularly when it had only been twenty years since Grover Cleveland (invoking the Monroe Doctrine) had rattled his saber at the U.K. over the Venezeulan border dispute. We might also look at the large number of Italians (about 3 million) who had emigrated to America in the period 1900-1915. Italy began World War One as an ally by treaty to Germany, but refused to enter the war -- then secretly negotiated to enter hostilities against Germany in exchange for territorial demands (which were not met). If three million new-minted Italian-Americans were taking their cues from their country of origin, it is by no means obvious what their opinions would be on American intervention in the war.

And immigrant populations like Irish-Americans or Italian-Americans were a constituent part of one of the largest and most crucial reasons for the non-intervention policy: the strange domestic political situation in America at the time of World War One. The