The United States of America is the most ethically diverse country by population. However the government is not diverse at all. Countries around the world have more diverse governments than the U.S. A country that is roughly 50% female has had no female leaders and a congress that is 81% male.
Politicians in the U.S. serve a wide assortment of different minority groups. Each group has its own needs; Mexican immigrants require different things than disabled people. When we have a government that is mostly white upperclassman we aren't really able to get any other perspectives besides a white upper class male's.
Part of this problem is that the voting turnout in the United State's is really low. But this is usually because they feel forgotten buy their government.
Another part of the problem is that both women and people of color face much more prejudice than their white male candidates. There are even recent examples of this happening during the current election campaign with Clinton and the past two with President Obama. Hillary Clinton has faced so much hate from the media on her appearance that male candidates would have never even thought of receiving. Trump has also taken advantage on the fact that she is the woman by saying she is not well suited or "does not have stamina." Obama has been called racial slurs, and many people even claim that he was not even born in the U.S.