The United States of America is not ruled by any one person or group, but rather by a system of government that is based on the principles of democracy and the rule of law. The United States is a federal republic, which means that it is composed of multiple states that have their own governments and laws, but are united under a federal government that has specific powers and responsibilities outlined in the United States Constitution.
The federal government of the United States is composed of three branches: the legislative branch (which consists of the Senate and the House of Representatives), the executive branch (which is led by the President), and the judicial branch (which includes the Supreme Court and other federal courts). Each branch has specific powers and responsibilities that are designed to balance and check the powers of the other branches, ensuring that no one branch becomes too powerful.
The President of the United States is the head of the executive branch, but the power of the President is also limited by the Constitution and the other branches of government. Ultimately, the United States is ruled by its citizens, who elect representatives to government positions and have the power to hold those representatives accountable for their actions.