Answer:
One major tenet of the United States system that is typically lacking in a parliamentary government system is the separation of powers. In the United States, the government is structured with three separate branches: the executive, legislative, and judicial branches. This separation is designed to ensure a system of checks and balances, preventing any one branch from becoming too powerful. In contrast, a parliamentary system often combines the executive and legislative branches, where the executive (Prime Minister) is drawn from the legislative branch (Parliament). This fusion of powers is a key distinction between the two systems.