Well, the US political system doesn't have enough parties. So instead of having parties which try and get votes by showing something the people want, the Koch brothers, and others, spend money telling the people what to think, and lots of them take it just like they get brainwashed by Coca-Cola, Pepsi, McDonalds etc.
I don't know if more parties would solve the problem, because they be m ore beholden to special interests. The real problem is that the primary system is so slanted towards early, smaller states most of have no say in who the major parties put up as a candidate.
The thing is, the money knows where to throw its money.
There are two issues in the US.
The first is politicians being bought. Now, they can be bought easily because they know that money buys an election easily in the US.
The second is that because there are only two viable parties which are covering such a large population, that they can't appeal to what the people want. Doing that would annoy too many people. They have to become generic.
Look at Germany. You have the right wing CDU/CSU. You have the left wing SPD, but then you have the environmentalists, Die Gruene, you have the FDP which is sort of center right which supports liberal policies, then you have the new AfD a much further right party. The German system has allowed a party like the AfD to spring up out of no where and to be doing quite well at it. Political mobility. Then you have Die Linke, further to the right.
There are six parties, each of them covers a part of politics.
In the US, the AfD, CDU/CSU and FDP are Republicans, the SPD, Die Linke and Die Gruene are Democrats. They try and fill the gaps where people who support these things would be by telling them what to think.
This means you have generic policies and people are voting for things they don't really want. But the Democrats will see this as a mandate because people voted for it.
This means that the money knows where to spend the money, because people can't be attracted by another party. They're either attracted by the Republicans or Democrats because the system says they're the only viable parties.
EVERY PR election in a proper functioning democracy has a wide number of parties in government. It's that simple. Germany is actually quite low at 6 and had less last time around.