There is nothing new in the world except the history you do not know.
Harry S. Truman 33d President of the United States.
All politics is local.
Thomas P. A "Tip" O'Neil Representative of 8th District Massachusetts
Most Europeans and Americans are not fully aware of how much state autonomy remains embedded in the Federal Constitution of the United States of America. The U.S. Constitution preserves the sovereignty of the states, and two reasons for the preservation are localism and the Articles of Confederation.
In U.S. law schools, a course in Constitutional Law is mostly taken up with studying cases of judicial review by the Supreme Court of challenges to the validity of particular exercises of state or federal government power under the Constitution. Broadly, the issue decided, more often than not, is whether the Constitution restrains state or federal government action. The Supreme Court uses several doctrines to decide that issue including substantive and procedural due process, equal protection, preemption, separation of powers, and federalism. These doctrines and the judicial decisions using them form the core of a U.S. Constitutional law course.
James E. Hickey,
Localism, History and the Articles of Confederation: Some Observations about the Beginning of U.S. Federalism, 9 Ius Gentium 5
Available at: https://scholarlycommons.law.hofstra.edu/faculty_scholarship/767