"automatic (i.e. reliable)"

I was in .mil. That word pairing is unfortunately an oxymoron. Reliable if you have a large army of non-elite skilled techs and contractors providing support, while totally unconcerned about what their system is doing to their friends and family back home. Even a sociopathic orphan would have to be concerned about how everyone else would likely treat quislings aka himself. Historically you really don't want to be the quisling, they historically tend to get worse treatment than the actual bad guys. MAYBE you could pull it off if you went all multicultural and made sure groups never fought against their own people. Maybe.

The first week would, indeed, be pretty rough on "the masses". Then again if the average lifespan of an elite is 80 years, lets say 40 remaining years on average, that means life will be pretty good for about a week and then they die having thrown away 39 years and 51 weeks of life. They're not dumb enough to try that unless pushed into a corner (perhaps literally, by rioters?) with a predicted lifespan under a week. Then a lifespan of a week or so starts sounding like an upgrade. Who knows, maybe the horse will speak after all (weird fable reference).

All you need is one domestic "wedding party" incident and next thing you know, its the modern equivalent of the claymores getting turned backwards into the compound and set off. If you think combat drones would be effective against a favella, imagine how much better they'd work against a landed estate when one techie gets pissed off and changes a few things.

Its hard to keep 999 people happy with a management style of "iron fist and no quarter". Street gangs can only pull off 9 or so and attempting 99 is a recipe for factional fighting and an elimination of the organization that allowed one guy to be in charge of so many. It just doesn't scale.

There are ways to implement an authoritarian regime, most of the successful ones historically did not find domestically created and applied technology to be a primary part of the strategy. Tangentially on the borders something or other helped or maybe made some activity more profitable, but not as a pillar of the strategy.

"Just masses of people won't do it anymore."

You need masses of people to fight when the other side also has masses of people. Think Germany in the 20s/30s when huge right wing groups were fighting huge left wing groups, before the right rose to power over the left and wiped them out. When the ratio is 1:100 or 1:1000, one side can have all the drones they want, but if the other side has one angry guy with a sniper rifle, they win. Rephrased, a war of attrition is a great battle strategy if both sides are roughly evenly matched, but when its 1:1000 or so, attrition is no longer a wise strategy, in fact its about the dumbest strategy I can think of. We have the neocons acting as quislings because they're dumb enough to think they'll get better treatment under the new regime if they're good little quislings today. But that's not going to happen to 30% or whatever it is of the population when it hits the fan, so that illusion will evaporate relatively quickly. Under realistic bad conditions, just aren't enough quislings to require masses of non-quislings to oppose them.

The threat to the apparent future American "regime change" isn't a crowd of hundreds of hippies occupying a park, but one angry dude with a sniper rifle. If one thing defines Americans its being ridiculously heavily armed compared to most other civilians, and the guy who buys a "scoped deer hunting rifle" and keeps it in his basement is much more of a deterrent than a hundred hippies waving signs in a protest march. An armed society is a polite society, so there is at least some hope for a peaceful future.

As an optimist I always hope humans will be smart enough to avoid the kind of stupid violence I see in history, and I often end up disappointed, especially when they're money to be made off violence (and I'm not talking about videogames, but the real thing). I'm not a fan of what I see on the horizon, but I'm not going to pretend to be blind just because I intensely dislike it and hope it can be averted.