At its peak, the KGB employed ~500,000 people directly, with untold more employed as informants.
The FBI currently employs ~35,000 people. What if I told you that the FBI could reach the KGB's peak level of reach, without meaningfully increasing its headcount? Would that make a difference?
The technology takes away the cost of the surveillance, which used to be the guardrail. That fundamentally changes the "political" calculus.
The fact that computers in 1945 were prohibitively expensive and required industrial logistics has literally zero bearing on the fact that today most of us have several on our person at all times. Nobody denies that changes to computer manufacturing technologies fundamentally changed the role the computer has in our daily lives. Certainly, it was theoretically possible to put a computer in every household in 1945, but we lacked the "political" will to do so. It does not follow that because historically computers were not a thing in society, we should not adjust our habits, morals, policies, etc today to account for the new landscape.
So why is there always somebody saying "it was always technically possible to [insert dystopian nightmare], and we didn't need special considerations then, so we don't need them now!"?