Am I being too cynical to think that if the person/group with this intelligence wants to move the United States in a certain direction, they can easily threaten, blackmail, or leak embarrassing/illegal information about those politicians/high-ranking military officers/CEOs of large corporations standing in their way.

I am not saying every powerful person can be blackmailed, threatened, or have career-ruining secrets, but even if you have the power to control the actions of 1% of those people, that's a pretty significant power.