The correct answer is it would end the electoral college system.
Currently, the United States uses the electoral college system in order to decide a president. In this system, states are assigned a certain number of electoral votes based on their representation in the House and Senate. This results in larger states (like California, Texas, New York) to have a large role in determing the presidency. However, it also ensures that the voice of smaller states is not overshadowed.
If the US switched to a direct popular election, the candidate with the most votes would win instead of the person who receives a majority of the electoral college votes. There would be no need for the electorate system anymore.