This depends upon how you define representation.
If you are asking about what is called descriptive representation, Congress is not very representative at all. This is because Congress does not really "look like" America as a whole. The percentage of women in Congress is much lower than the percentage of women in the population as a whole. So is the population of minority groups. Most of all, the membership of Congress is much wealthier than the population of the US. In these ways, Congress is not very representative of the country as a whole.
If you are asking about ideological representation, Congress is much more representative. Major points of view among the population are generally well-represented in Congress. There is no ideology that is strongly held in the US but which is not represented by the parties in Congress.