The election and reelection of Barack Obama was historic

The election and reelection of Barack Obama was historic because, among other reasons, he was the first African-American and non-white male President elected in American history. However, we still have not had a female President elected to office, as Donald Trump defeated Hillary Clinton.

Women make up more than half of the American population, and women have been elected as President or Prime Minister in a number of countries in the past, including the United Kingdom, India, Pakistan, Germany, Israel, South Korea, Australia, the Philippines, and Liberia. Currently there are six female declared candidates running in the Democratic Party primary for the 2020 Presidential election.

In your opinion, why do you think we have never had a female President in the United States? What would need to change for a female President to get elected?