Winning a war isn't about force: it's about morale and mindset. If you can't stop people from fighting against you, you can't win a war. A drone has never walked into a community and gotten people to put down their guns.
Drones are weapons. They're one of the many tools of war. But war has always been about culture, food, politics, religion, demographics, and many other factors.
People win and lose wars. Weapons help.
Drones on the other hand are cheap and require fairly few people to operate. A few deaths squads in the control might be enough to suppress an entire country.
It's a little like surrounding an army on an open field: If you give the losing side in a pitched battle an escape route, many of them will run, but if you surround them, they will fight to the death because there's nothing else they can do.
While it’s not exactly that straightforward but democratic reforms is what basically killed it. Gorbachev allowed independent power centers to form which weren’t controlled by the party apparatus and these new centers had no reason to preserve the union/empire even though relatively few people (outside of the Baltic region and the Caucasus) actually wanted to abolish it. Internationalist empires like the USSR, Austria-Hungary, Ottomans, Tsarist Russia (outside of the core regions), Yugoslavia and even Rome to some degree tend to be very fragile. Any rapid attempt to reform the system tends to destabilize it to such a degree that it can no longer survive without extreme violence.
China and the US (still) are nation states and not real empires, therefore they are almost immune to some of the issues which brought down most historical empires (nation states are much better in enacting reforms and generally much more flexible). Of course that’s not permanent and might change in a generation or two, for instance if different US states continue drifting apart economically, culturally and socially.
It's entirely possible our technology progress has surpassed the government Great Filter and it is now almost impossible for empires to crumble from within e.g. CCP has experienced many "empire-ending" problems but still somehow survived to this day.