Why do I make this outrageous sounding claim that the USA is not a democracy ? Because it is a flawed democracy and the flaw is so huge it undermines the democratic process itself. Please let me explain. The US has forgotten one simple piece of common sense: "Whoever pays the piper, calls the tune." And in the USA, the politicians are paid. The guys paying them are controlling what they do and say and how they vote.
It comes about because each politician believes that he/she needs to advertize on television. The is expensive and outside the budget of the majority of politicians. So they require donations in order to advertise themselves on TV. These donations are huge and come from corporations and businesses who want to have a voice, indeed a vote, in Congress. These are called "soft money" donations and go indirectly to the candidate via a super PAC. But don't doubt that the candidate is made very aware of who he/she is now working for. The vote so purchased may be shared between several corporations who negotiate between themselves how their vote will be used and what their man or woman will say in Congress.
It is completely irrelevant whether the politician is a Democrat or a Republican, that is just a layer of paint as it were. The politician belongs to and represents solely the corporations that paid for his/her TV advertizing. The electorate don't count because that is a vote, it is not money.
Now what can the USA do about this ? Well you can't work within the system because once a politician has accepted "soft money" they will never vote not to. The only possibility is to set up a grass roots movement that must become nationwide and at each election have candidates that don't advertize on TV. They can have public meetings and get their message across through conventional use of the media but without TV advertizing. And the message throughout is that if a candidate has a TV advert, that politician will never do more than lip service to his electorate. He/She just works for the corporations that paid for his/her TV adverts.