Traditionally, researchers of American identity have mostly focused on only two components of American identity: liberalism (America as a land of freedom and opportunity) and ethnoculturalism (America as a nation of white Protestants).
In recent years additional dimensions of American identity have been considered. Two newly overlooked elements of American identity are civil republicanism (America as a vibrant participatory democracy with dutiful citizens) and incorporationalism (America as a diverse nation of immigrants).
The content of American identity: Rooted in liberalism
Recent scholarship has identified complex and often competing components of American identity that are rooted in the widely accepted liberal tradition, civic republican tradition, the contested ethnocultural tradition, and the equally contested incorporationist tradition. This perspective has been termed the "multiple tradition" or multiple conceptions model of the content of American identity.
Liberalism, in short, is the image of America that comes most easily to mind when people think about what it means to be American and is widely seen as the defining essence of American political culture. It stresses minimal government intervention in private life and promotes economic and political freedoms along with equality of opportunity.
Ethnoculturalism has also been a defining element of American identity. It sets boundaries on group membership. In its extreme, ethnoculturalism maintains that Americans are white, English-speaking Protestants of northern European ancestry. Over time this tradition has been discredited, but it is far from breathing its last breath.
Civic republicanism emphasizes the responsibilities, rather than the rights of citizenship. It advances the notion that the well being of the community is more than just the sum of individualistic pursuits of private gain. Rather, a vibrant self-governing community needs individual members to act on its behalf. In his view, we should all be involved in social and political life and pursue ends that serve the public good. As Tocqueville noted, pursuing the public good engenders pride and patriotism, which further motivate people to "labor for the good of the state".
Incorporationalism is a more recent tradition to the set of norms that constitute the content of American identity. The seeds of this tradition were planted nearly a century ago with cultural pluralism, and only in the past few decades have both elites and citizens come to endorse this notion that America's unique identity is grounded in its immigrant legacy and in its ability to convert the challenges immigration brings into thriving strengths. Ethnoculturalism continues to exist, but it does so alongside an incorporationist challenge that has grown stronger over the years due to many factors, including rights-based movements of the 60s and 70s and the political incorporation of immigrants and their descendents.
The simplicity of incorporationism - the idea that the United States is a nation of immigrants - belies complex beliefs about the balance between unity and diversity. While there are people who advocate one extreme of complete assimilation and others reject the premise of assimilation altogether, most Americans do not fall at these extremes. Incorporationism celebrates Americans ability both to assimilate and maintain difference.
The above mentioned elements can make the concept of American Identity which can be studied and measured each separately and widely.