After Hoover died it became clear the level of actual corruption and control he had over Presidential elections, and how the FBI had been suborned to serve his

After Hoover died it became clear the level of actual corruption and control he had over Presidential elections, and how the FBI had been suborned to serve his personal and political beliefs. So there was a secret police period, except it was years ago and it didn't result in a totalitarian system. That did include the mass interception of mail and telephone calls, without the pesky need for warrants. What has happened is a relatively short period of time in which technically inclined Americans had access to a mass communication medium which was extremely difficult to intercept. Apart from that period of time it has always been the case that if the Government wanted to get you it could and would intercept your communications. The general public have probably just always operated on the assumption that their lives just aren't important enough to become the centre of attention.