How does US representative democracy differ from Athenian direct democracy?

In the US, citizens vote, while in ancient Athens, only the Council of 500 voted to pass laws.
In the US, citizens elect representatives to office, while in Athens, elections were not held.
In the US, citizens run the government, while in Athens, citizens elected officials to run the government.
In the US, anyone can participate in Congress, while in Athens, only citizens could hold offices.