"The great rule of conduct for us, in regard to foreign nations, is in extending our commercial relations, to have with them as little political connection as possible. Europe has a set of primary interests, which to us have none, or a very remote relation. Hence she must be engaged in frequent controversies the causes of which are essentially foreign to our concerns. Hence, therefore, it must be unwise in us to implicate ourselves, by artificial ties, in the ordinary vicissitudes of her politics, or the ordinary combinations and collisions of her friendships or enmities."
In his inaugural address in 1801, Thomas Jefferson crystallized this American policy in more familiar words, promising: "peace, commerce, and honest friendship with all nations, entangling alliances with none."
Protecting a revolution in a counter-revolutionary world, and promoting it
Besides being emotionally appealing, the ideas of independence and isolation defined an extremely practical, protective policy for a country that was relatively small, poor, and weak. Avoiding entanglements with others was really more about hoping to keep other more powerful states from getting entangled with us, and the tactic was mostly successful. The less powerful were another matter entirely.
But even as American revolutionaries chose a protective isolationism for their state, they promoted their revolution as a universal benefit. The Declaration of Independence (1776) is rooted in the universal right of all people to establish "the separate and equal station to which the Laws of Nature and of Nature's God entitle them." From the beginning, the exceptional American "right of one people to dissolve the political bands which have connected them with another" was established as a global entitlement -- but not one without internal contradictions.
This evangelism of freedom remains one of the strongest themes in the idea of American exceptionalism, serving as both inspiration and/or excuse for the international entanglements we at first set out to avoid. Early on we saw ourselves as leading by example, as Jefferson articulated in his farewell address (1809), calling the United States an "empire of liberty," a governmental model for others to imitate:
"Trusted with the destinies of this solitary republic of the world, the only monument of human rights, and the sole depository of the sacred fire of freedom and self-government, from hence it is to be lighted up in other regions of the earth, if other regions of the earth shall ever become susceptible of its benign influence."
This almost religious sentiment was already at odds with the American reality of westward expansion, not least in the extra-constitutional purchase of Louisiana from France (1803). Acquiring Louisiana roughly doubled the size of the United States, headed off war with France, and put a territorial wedge between the Spanish holdings in America. The purchase turned the U.S. into one of the largest countries in the world, but it wasn't exactly a boon to the freedom and self-determination the people who lived there, despite their theoretical entitlement by the Laws of Nature and Nature's God. Instead, Louisiana became susceptible to the benign influence of freedom and self-government by being subjected to and by the United States.