This book analyses the fundamental aspects of the Constitution of the United States of America. This book analyses the fundamental aspects of the Constitution of the United States of America, which has proven to be a reality in motion and with an ‘exceptional’ capacity to adapt to the rapid and profound changes that have occurred in over two centuries in American society and economy. The book aims to better understand how the constitutional text has evolved up to our times. The 27 amendments to the Constitution, the interpretation of the Supreme Court and the particular political system have ensured that the constitutional system has not undergone major institutional upheavals. Thanks to the contribution of the many authors, the book offers valuable insights into a constitutional system that still reveals an extraordinary relevance. This can be considered an added value to studies in the field of comparative law. 1 Profiles of Constitutional History of the United States of America (Claudio Martinelli); 2 The Challenge of Formal Amendment in the United States (Richard Albert); Introductory Note to the Form of Government (Guerino D’Ignazio); 3 Design, Evolution and Interpretation of Checks and Balances in the American Constitution (Andrea Buratti); 4 Congress (Davide De Lungo); 5 The Public Administration in the System of Separation of Powers (Guerino D’Ignazio); 6 Sovereignty and Federalism (Andrea Pin & David Kenny); 7 Federalism and the Welfare State (Andrea Pierini); 8 Fundamental Rights and Freedoms (Paolo Passaglia); 9 The Supreme Court (Chiara Bologna); 10 The Judicial System (Angioletta Sperti); 11 Protecting the Constitution against the States? The Importance of the ‘Guarantee Clause’ in a Comparative Law Perspective (Giuseppe Martinico); About the Authors