Because the framers of the US Constitution were concerned about citizens having too much power, they

banned citizens from voting.
organized a system of consuls and magistrates.
established a republic.
created a system of independently governed city-states.

established a republic.

The framers of the US Constitution were indeed concerned about citizens having too much power. As a result, they did not ban citizens from voting, but instead established a republic. This means that power is held by the people through elected representatives. Through a system of checks and balances, they aimed to prevent any one individual or group from controlling the entire government. Additionally, they did not create a system of independently governed city-states like Ancient Greece, but rather organized a system of consuls and magistrates, which are executive and judicial officers respectively, to ensure a separation of powers.