How is government in the United States today different from government in ancient Athens?

The United States is a direct democracy.

The United States allows citizens to vote.

The United States is a republic.

The United States has a bicameral legislature.

The best option would be that " The United States is a republic", since a Republic always implies that most of the legislative power comes from elected officials, and in Athens every citizen could vote directly on issues.

The correct answer is The United States is a republic.

The Athenian state was actually a direct democracy while the US is a representative democracy. Citizens are allowed to vote in both states, and both also have a bicameral legislature. The difference is that the United States are a republic whereas the Athenian state was a city-state meaning that they didn't have a vast land and representatives to represent various parts of the land and people from that area.