American nationalism is a form of civic, ethnic, cultural or economic influences found in the United States. Essentially, it indicates the aspects that characterize and distinguish the United States as an autonomous political community. The term often explains efforts to reinforce its national identity and self-determination within its national and international affairs.

All four forms of nationalism have found expression throughout American history, depending on the historical period. The first Naturalization Act of 1790 passed by Congress and George Washington defined American identity and citizenship on racial lines, declaring that only "free white men of good character" could become citizens, and denying citizenship to enslaved black people and anyone of non-European stock; thus it was a form of ethnic nationalism. Some American scholars have argued that the United States government institutionalized a civic nationalism founded upon legal and rational concepts of citizenship, being based on common language and cultural traditions, and that the Founding Fathers of the United States established the country upon liberal and individualist principles.

The United States traces its origins to the Thirteen Colonies founded by Britain in the 17th and early 18th century. Residents identified with Britain until the mid-18th century when the first sense of being "American" emerged. The Albany Plan proposed a union between the colonies in 1754. Although unsuccessful, it served as a reference for future discussions of independence.

Soon afterward, the colonies faced several common grievances over acts passed by the British Parliament, including taxation without representation. Americans were in general agreement that only their own colonial legislatures—and not Parliament in London—could pass internal taxes. Parliament vigorously insisted otherwise and no compromise was found. The London government punished Boston for the Boston Tea Party, and the Thirteen Colonies united and formed the Continental Congress, which lasted from 1774 to 1789. Fighting broke out in 1775 and the sentiment swung to independence in early 1776, influenced significantly by the appeal to American nationalism by Thomas Paine. His pamphlet Common Sense was a runaway best seller in 1776, read aloud in taverns and coffee houses. Congress unanimously issued a Declaration of Independence announcing a new nation of independent states had formed, the United States of America. American Patriots won the American Revolutionary War and received generous peace terms from Britain in 1783. The minority of Loyalists (loyal to King George III) could remain or leave, but about 80% remained and became full American citizens. Frequent parades along with new rituals and ceremonies—and a new flag—provided popular occasions for expressing a spirit of American nationalism.

The new nation operated under the very weak national government set up by the Articles of Confederation, and most Americans prioritized their state over the nation. Nationalists led by George Washington, Alexander Hamilton, and James Madison had Congress call a constitutional convention in 1787. It produced the Constitution for a strong national government which was debated in every state and unanimously adopted. It went into effect in 1789 as the first modern constitutional liberal democracy based on the consent of the governed, with Washington as the first President.

In an 1858 speech, future President Abraham Lincoln alluded to a form of American civic nationalism originating from the tenets of the Declaration of Independence as a force for national unity in the United States, stating that it was a method for uniting diverse peoples of different ethnic ancestries into a common nationality:

If they look back through this history to trace their connection with those days by blood, they find they have none, they cannot carry themselves back into that glorious epoch and make themselves feel that they are part of us, but when they look through that old Declaration of Independence they find that those old men say that "We hold these truths to be self-evident, that all men are created equal", and then they feel that moral sentiment taught in that day evidences their relation to those men, that it is the father of all moral principle in them, and that they have a right to claim it as though they were blood of the blood, and flesh of the flesh of the men who wrote the Declaration, and so they are. That is the electric cord in that Declaration that links the hearts of patriotic and liberty-loving men together, that will link those patriotic hearts as long as the love of freedom exists in the minds of men throughout the world.

— Abraham Lincoln, address to Chicagoan voters, July 10, 1858