There are three main sociological perspectives, each of which would have a different take on why there are so few women in positions of power in the American political system.
The first perspective is structural functionalism. This perspective holds that societies are like organisms and that each part of a society generally plays a role in keeping that society stable and healthy. From this perspective, we might argue that women have been excluded because keeping women out of power makes it more likely that women in general will do things that our society needs like staying home with children. Thus, exclusion of women could be beneficial to our society. This perspective might also say that the exclusion of women is simply a dysfunction. It might argue that the family is necessary to society, but that it has led to the exclusion of women from power even though that is bad for society.
The second perspective is the conflict perspective. In this perspective, the cause of the exclusion is much clearer. Women and men are different groups of people and they are in conflict with one another. Men have won in this conflict and have excluded women from power.
The final perspective is symbolic interactionism. This perspective says that we act in ways that are based on the meanings we assign to things. In this perspective, the exclusion might be caused by women perceiving politics as a dirty business that they do not want to be involved with. Alternatively, it might come from voters perceiving women as incompatible with politics.
Each of these perspectives, then, has a different point of view on this topic.