Re: "lucky few [etc]"
As we are finding out, the checks and balances we thought we had are mainly just people's own self-control.
The main problem with the American model of checks and balances (and, indeed, any other such system) is that it relies on a delicate balance between the speed at which the system is disturbed (by, say, a President who wants more power) and the speed at which the checks and balances can push back against the disturbance.
When the US Constitution was framed, that balance of speeds was a reasonable thing to assume, although it wasn't perfect even then. Today, however, if one of the participants, especially the President, decides to steamroller the boundaries of his power, the checks and balances cannot keep up, since the tools at their disposal haven't really caught up with the evolution of technology. (You can easily break the system with repeated use of "the weaponized tweet", but that's a poor tool for fixing it.)