ATLA

Who the frick was going to tell Bumi he couldn't call himself king?

Maybe, but ultimately doesn't that just reinforce the theory that the authority of the Earth King is institutionally weak by design? Let's assume just for the sake of argument that the Dai Li are cooperative and not glowrockies that have seized the mechanisms of government because that's a whole other issue altogether:
>Fire Lord Sozin conquers and colonizes territory on the coastlines: the Earth King either won't or can't do anything about it, it takes the Avatar's intervention to stop any further landgrabs
>Fire Lord Azulon sends his son General Iroh to siege Ba Sing Se for 800 days (roughly two years): the besieging Fire Nation army is deep inland into the continent, and even if they hold coastal territories, not a single Earth King army tries to break the siege from the outside
Underneath the surface level parallels of the Hundred Years War mirroring the Imperial Japanese invasion of China in the 20th Century, the actual mechanics of the war reminds me more of the England vs. France Hundred Years War, where a smaller but more unified and competent island kingdom was able to make lots of initial gains on a larger continental foe because the continental kingdom was decentralized, and each territory was more interested in preserving themselves at the expense of their neighbors instead of presenting a united front against an aggressive invader.

See this is where we need to stop analyzing the military actions since it's plainly obvious it wasn't considered in enough detail to justify the state of the world. Frankly what we see Earth Benders capable of should absolutely devastate Fire Nation armies if they ever came up against a force of Benders.
>Every Earth Bender can function as catapult and a tower.
>Tunneling to move under cover, and infiltrate or lay traps
>Destablizing the ground into quicksand and sucking people under.
>Whisper-quiet maneuvers to isolate and abduct individuals.
>Earth Benders have been seen to out-manuver tanks
>They can coat themselves in hard rock/crystal/candy armor, to resist weapon blows and fire blasts
>Toph at the very least is capable of covering distances using the Road-Runner style to lift the road off the ground and moves at a speed comparable to a skybison
Just these factors alone should be enough to make terrifying counter-attacks. Teams of bender shock troops that could easily route fire nation forces. But we don't hear about them. Hell we only have one organized Loyalist Earth Bender team who were used to show how badass the Drill was.

I think we need to chalk that up to it being like the 5th episode. The history of China is civil war so even though Chin isn't called "The Usurper" or "Rebel" it definitely fits the parallel for him to have been.

To the point we get it established later that Kuei 52nd Earth King. Not 52nd "King of Ba Sing Se", "or the SwallowtailOtter Dynasty" just "Earth King". It'd be worth mentioning if the kings had such a short lifespan 51 came and went since the time of Kyoshi.

>the kings had such a short lifespan 51 came and went since the time of Kyoshi
The writers have always had a terrible sense of timescale, but you could justify it by assuming the Earth Kingdom underwent several eras of great instability. Like Imperial Rome had
>the year of 4 emperors (AD 69)
>the year of 5 emperors (AD 193)
>the year of 6 emperors (AD 238)
That's 15 monarchs accounted for. Throw in a few more palace coups, early retirements, ambitious pretenders to the throne, hunting accidents and hunting """accidents""" and its easy to hit 51 by the time Aang wakes up from the iceberg.

I don't see any reason to assume the title of Earth King didn't exist before Kyoshi. And Chin never took Ba Sing Se, so the royal line presumably wasn't broken by his conquest. I would assume the situation was something akin to Kuvira where Ba Sing Se was politically weak for one reason or another and so some conqueror rolls through and gobbles up all the disorganized vassal states until he comes up to the Avatar's doorstep and gets smacked down.
Really, Kuvira's story is basically just the Netflix version of Chin's conquest. It even has Chin recast as a stronk woman and the Avatar raceswapped to be browner.

>it still wouldn't fit all that well unless the Ba Sing Se Royal line was delusional and calling themselves kings of the nation when it wasn't true

Nonsense, why would the Earth King abandon his title just because some upstart is gobbling up the provinces? It's a bit delusional once Chin's conquered everything outside the capital, but the Earth King has every motivation to continue calling himself the rightful ruler of the Earth Kingdom until the day Chin kicks down his door.

>Because a king that came along later and swept up Chin's leavings to actually do that would definitely give themselves a new title.

First, there's no reason why someone taking over after Chin couldn't or wouldn't just assume the title of Earth King to emphasize their legitimacy. I wouldn't have been surprised if Chin would've started calling himself the Earth King if he'd ever managed to take Ba Sing Se.
Second, the position of Earth King never actually changed hands. Presumably after Chin's death, his territories and armies fell into disarray and the Earth King at the time was able to reestablish control.

Well there's a difference between being a king and being THE Earth King. Really, it comes down to motivation. Kuvira actively wanted to sweep away the old, archaic trappings of feudalism and royalty and establish something new, so she changed the names. Someone else might have less idealistic motives and desire the legitimacy that the old titles hold, so they just usurp the title of Earth King.