The belief that foreign countries can possibly get an agent into the Presidency is absurd. Thinking that he would then be able to disband the military or anything else along those lines is pure Hollywood.
Having agents in the FBI or CIA is a far cry from having one in the Presidency. If it were so easy, then why haven't Russian agents run the intelligence agencies?
And, of those spies you point to within the CIA and FBI weren't quite a few American? Of course, so being born in America has absolutely nothing to do with their level of security risk.
But hey, if you guys really think this way there's obviously nothing anyone can say to convince you otherwise. After all, if I tried, perhaps it was because I am really an agent of the enemy.