One of the most frequent characterizations of US foreign policy in the 18th and 19th centuries is that it was isolationist. In 1796, when he decided not to run for a third presidential term, George Washington wrote (possibly with the help of Alexander Hamilton) a farewell address to public life. In one of the most quoted parts of this speech, Washington said that “It is our true policy to steer clear of permanent alliances with any portion of the foreign world.” Quite similarly, in 1821 John Quincy Adams warned that the United States should not “[go] abroad, in search of monsters to destroy.” We can also cite Thomas Jefferson, who in 1799 declared that “Commerce with all nations, alliance with none, should be our motto.” Finally, in 1823 James Monroe declared (with great help from the aforementioned John Quincy Adams) that “The political system of the allied powers [of Europe] is essentially different (…) from that of America.”
In short, it is by all the above (and other) quotations that historians often classify American foreign policy in the 18th and 19th centuries as isolationist. This trend, it follows, was altered in World War I by Woodrow Wilson, who broke away from traditional isolationism to lead the United States to fight in Europe. More than that: at the end of the war, in his 14 Points, Wilson proposed the creation of the League of Nations, a permanent multilateral international organization, with the objective of promoting the collective security of the member countries. The Wilsonian tendency was reversed by Republicans in the 1920s and 1930s, mainly because they refused to join the League of Nations, opting for isolationism. However, Woodrow Wilson’s proposal was retaken by Franklin Delano Roosevelt in World War II. The United States defeated the enemy forces in Europe and the Pacific and in the end war was one of the main founders of the United Nations, an international organization created to replace the League of Nations. Since then the United States has predominantly adopted Woodrow Wilson’s perspective and avoided the isolationism of the Founding Fathers and of the Republican presidents of the interwar period. Only ultra-conservatives believe and advocate that the US should retake the foreign policy of George Washington, Thomas Jefferson, John Quincy Adams, and James Monroe. However, all this evaluation already starts flawed when it characterizes American foreign policy in the 18th and 19th centuries as an isolationist. To explain why, we can differentiate two terms: isolationism and unilaterialism.
Predominantly, US foreign policy in the 18th and 19th centuries followed George Washington’s advice “to steer clear of permanent alliances with any portion of the foreign world.” However, it should be noted at the same time that this foreign policy followed Thomas Jefferson’s advice to establish “commerce with all nations.” In other words, despite the lack of permanent alliances with other countries (particularly European ones), what the United States did not lack in that period was a growing trade with other parts of the world, in addition to regular diplomatic contact (although not characterized by permanent alliances). To call this isolation is to force language too much. There are many historical examples of countries that have actually isolated themselves from the rest of the world: Japan between the 17th and 19th centuries, China between the 15th and 19th centuries, Paraguay from 1811 to 1844, and more recently North Korea are just a few. US foreign policy in the 18th and 19th centuries would be better characterized as unilateralist or non-interventionist. This means simply that the US didn’t subject its international relations to foreign authority.
There was no US isolation before the 20th century. What happened was a policy of avoiding permanent alliances. Meanwhile, the country had no problem with expanding its diplomatic contacts and its international trade (although some economic protectionism was practiced, but I leave this subject to another time). The same can be said about the attitude taken by the presidents in the interwar period: not participating in the League of Nations did not mean isolation from the rest of the world, quite the opposite: the US actively participated in the economy and international politics at that time. It just did not do this through the international organization proposed by Woodrow Wilson. It is perfectly possible to participate actively in international relations unilaterally, i.e. without the formation of permanent or binding alliances with multilateral international organizations.
Confusing the terms isolation and unilateralism may just be an oversight or an evaluation error. But it can also be a purposeful strategy. Confusing the terms may hide an undeclared requirement (or assumption): the only accepted international participation is that made through multilateral international organizations such as the League of Nations or the United Nations. No other is good enough. In this way, those who characterize US foreign policy before Woodrow Wilson as isolationist are severely limiting the possibilities for US international participation.