How does federalism differ from unitary government and a confederacy? How would politics and policies be different in America if there were a unitary system instead of a federal system? Or a confederation instead of a federal system? Additionally, explain the difference between dual federalism and cooperative federalism. 

100 words. 
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We generally speak of three forms of governmental structures”federalism, unitary government, and confederation. Federalism is a way of organizing a nation so that two or more levels of government have formal authority over the same area and people.
Chapter 3 explores the complex relationships between different levels of government in the United States. It describes the ways that the federal system has changed over two centuries of American government and why American federalism is at the center of important battles over policy.
Federalism is not the typical way by which nations organize their governments; there are only 11 countries with federal systems. Most governments in the world today are unitary governments, in which all power resides in the central government. Although American government operates under a federal system at the national level, the states are unitary governments with respect to their local governments. In the United States, local governments are legally creatures of the states: they are created by the states and can be changed (or even abolished) by the states.
In a confederation, the national government is weak and most or all of the power is in the hands of its components (such as states). The United States was organized as a confederacy after the American Revolution, with the Articles of Confederation as the governing document. Confederations are rare today except in international organizations.
The concept of intergovernmental relations refers to the entire set of interactions among national, state, and local governments in a federal system. The American federal system decentralizes our politics. For example, senators are elected as representatives of individual states and not of the nation. Moreover, with more layers of government, more opportunities exist for political participation; there are more points of access government and more opportunities for interests to be heard and to have their demands for public policies satisfied.
The federal system not only decentralizes our politics, it also decentralizes our policies. The history of the federal system demonstrates the tensions that exist between the states and the national government about who controls policy and what it should be. Because of the overlapping powers of the two levels of government, most of our public policy debates are also debates about federalism.
The American states have always been policy innovators. Most policies that the national government has adopted had their beginnings in the states. In many ways, the states constitute a national laboratory to develop and test public policies.