The root of the discontentment is not a Democrat vs Republican, nor a liberal vs conservative argument. It is the fact that politicians are beholden to the whims and direction of the corporate elites who finance their campaigns, the lobbyists who dictate which bills to support.
Politics in most of the Western world, i.e. the issue is not unique to the USA, is driven and subservient to transnational corporations and the billionaires who profit at every turn. Unfortunately a very large proportion of the populations work for these interests because that is the only source of income that they can earn.
Peel back the curtain and see how the military-industrial complex is profiting from the military misadventures. It is not about winning wars. It is about making ever greater profits. See how every gallon of gas you buy serves the interests of the mega-corporations. See how every time you buy a name brand product you are subsidizing another mega-corp.
Yelling at elected politicians is futile. They only say what they need to get elected and then they turn their backs and follow the orders from the lobbyists and in turn their paymasters.