What were the causes and consequences of the public's disillusionment with the federal government in the 1970s and 1980s?

Presidential corruption and lying

Vietnam, Watergate, conflict with Iran, and the revelation of coups and funding of rebels through the Nixon--Reagan presidencies caused citizens to become more cynical of the government. The average citizen began to believe that the government could be expected to lie and cheat their way through politics meanwhile putting American lives in danger.

The consequences of this resulting in citizens not believing their leaders or not knowing who to believe. Presidencies have been criticized more and citizens are not surprised when scandal occurs. This has led to elected presidents who are "outsiders" or lack political experience such as Jimmy Carter or Donald Trump.