The biggest difference in citizen participation in government between ancient Athens and the modern United States is:
US citizens elect officials to represent them in government.
In ancient Athens, direct democracy was practiced, and all eligible citizens had the opportunity to participate directly in the decision-making process, often in the form of voting on laws and important decisions in the General Assembly. In contrast, in the modern United States, citizens typically elect officials (representatives) to make decisions on their behalf in government. This representative democracy allows citizens to have a voice in the selection of their leaders but delegates the day-to-day decision-making to elected representatives.