Final answer:
Congress is tasked with establishing the federal courts beneath the Supreme Court, as mandated by Article III of the Constitution.
Step-by-step explanation:
The entity charged with establishing the federal courts beneath the Supreme Court is Congress. The judicial power of the United States shall be vested in one Supreme Court, and the Congress may from time to time ordain and establish in inferior courts. This in accordance with article III of the constitution.
This gives Congress the discretion to determine the shape and structure of the federal judiciary.
While the President does have the role of nominating judges, including those for the Supreme Court and the lower federal courts, these appointments must be approved by the Senate.
Moreover, although the President's role is crucial in nominating justices and federal judges, the actual creation and organization of the courts beneath the Supreme Court is the responsibility of Congress.
It was the Judiciary Act of 1789 that established the United States Court System, comprised of District Courts and Circuit Courts, with all federal judges holding their offices for life, barring impeachment, and receiving protection against salary reduction to maintain judicial independence.