The fact that Mr. Smith has the intestinal strength to stand up to special interests in the film reflects how entrenched corruption is in American politics. The machine way of doing things is shown to be politically corrupt, and not reflecting the interest of the people. This violates American ideals in that the theoretical system designed by the framers was intended to be representative of the needs and desires of the people. The machine form of politics shown in the film represents the needs of the few at the cost of the many. At the same time, the idea of Mr. Smith speaking on behalf of the many and being seen as a politician going against the norm is another example of how the corruption in the film violates American political ideals.
In the film, corruption is shown in a number of ways. First of all, the way that Mr. Smith gets into Congress is corrupt. He is chosen by machine bosses who want someone in Congress who will obey them. Second, you can see it in how the machine frames Mr. Smith, claiming that he owns the land that he is trying to put the camp on. They do it because they want the land for a corrupt deal they have going on dam construction.
These kinds of things violate American ideals because we believe that our political leaders should be elected by the people and should not use their offices to make themselves rich. Political machines took government out of the hands of the people and used it for the benefit of the machine bosses.