Federalism
The United States Constitution outlines the specific powers granted to the national government. In addition to these expressed powers, the national government also has implied powers. These are powers which are not stated directly, but are necessary in order to execute the expressed powers. The national government also possesses inherent powers, which it obtains through its status as a sovereign nation.
Any powers not directly granted to the national government are delegated to the state governments. Certain powers, like the power to levy taxes, are shared between the national level and state level of government. Other powers are are denied to both levels, like the power to grant titles of nobility.
Although the flexibility of this system allowed the Federalists and Anti-federalists to compromise, it has also led to conflict throughout history. There have been countless debates and even a Civil War over the distribution of power between the national and state governments.