I have not lost faith in the American public, but I have lost much faith in most of the leaders. As for the conclusion that the US is an oligarchy, it is not baseless, and in fact I did not jump to that conclusion.
There are many wise observers of the political situation in the US, both on the left and on the right, who tell us that to a great extent, the US is descending into oligarchy. It may not be totally obvious, but a cursory view of certain trends supports that assertion.
To a great extent, the laws benefit those in the upper income group. The ever-widening wealth gap is one example. The recent tax law is just the latest and clearest example of how the government is no longer "for the people," but for the elite.