How much impact does the average American have on public policy?

The statement comes from this Tedx Talk. The segment starts at around 8:30, and he talks about how a tiny minority of the economic elite decide all policy changes, mainly through controlling which candidates we are able to choose from. The actual statement comes at about 9:45. Here is a text source that says the exact same thing as whats in the Ted Talk.

Also, in what ways could this be good or bad for the country as a whole?