In many ways, these two perspectives provide opposing views on American politics. Functionalists note that American (or really any) society is characterized by a wide variety of interests. These interests are ideological, cultural, economic, and so on. The purpose or function of politics and political systems is to manage these competing interests in such a way that the overarching needs of society are met. Many Americans decry the way that special interest groups tend to dominate politics at the federal and state level. Some (but not all) functionalists would argue that this is actually healthy—in politics, competing interest groups vie for their own interests, and the result is policy that represents a wide variety of interests. The function of government is to facilitate compromise.
The conflict perspective of government emphasizes the mutual antagonisms between both interest groups and social classes in the United States. Conflict theorists acknowledge the role of government in mediating conflict, but they do not view this as a good thing. Rather, they emphasize that government is controlled by a dominant interest—economic interests in particular—that use power to crush efforts at achieving meaningful change. A conflict perspective on the healthcare debate, for example, would emphasize the ways that lobbyists for insurance companies and other corporations stand in the way of creating a universal healthcare system. Whatever "consensus" is produced by the government is not maintained by a rational system of competing interests, but by power.
Functionalism posits that the government has several basic, utilitarian functions and focuses its attention on the creation of institutions to manage these functions. In the functionalist view, the responsibilities of civil administration include law and order, security and foreign affairs, and social planning. Above all else, functionalists seek to manage conflict by working towards basic, majoritarian policies supported by a wide consensus of the body politic. Change, from the functionalist perspective, can be destabilizing.
Conflict theory, in contrast to functionalism, sees change as necessary and incumbent for the resolution of entrenched inequalities that exist in social and economic relations. Conflict theorists posit the existence of disparate classes and support active remedies to "flatten" society into a more egalitarian structure.
One example of the dichotomy between functionalism and critical theory in American politics is the system of financing political campaigns. Functionalists might perceive the infusion of money into politics as a method of guaranteeing engagement and cooperation of the less numerous financial classes. Critical theorists, meanwhile, would perceive the restraint of this influence as a normative goal advancing their ultimate objective of unseating the so-called "power elite."