Thinking about how Kusakihara said he doesn't consider Fodlan a continent and tried to make sure it was never called a continent, only for the English localization to immediately call it a continent in advertising and within the first half hour of the game
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Besides the fact that it's extremely funny how the fandom at large just calls it a continent anyway, it also is genuinely a fascinating look at what his thought process was, and how a lot of it boils down to "yeah this sounds cool."
Because think about it. Does he have a grand design in saying Fodlan isn't a continent? Was he going for a Christendom thing with Fodlan, where it's multiple different countries/lands all following an explicit rule set from a religious power?
Well, not really, since we see from the game itself that that comparison doesn't work. Leicester began with no approval from, crowning by or strict adherence towards the Church of Seiros. No matter how angry Rhea got about it when yelling at Claude in Three Hopes, it doesn't change the fact that it started and maintained itself as a kingless nation with no rulers and explicitly no religious power from its own church branch. For three entire centuries. And Adrestia booted out its own church branch a century before the game began with no lasting repercussions.
"But doesn't Rhea call Edelgard and the empire rebels after she starts her war?"
Yes, she does. However, authority is not a strict "X party controls Y party." Again, Rhea does not have supreme authority... over any of the countries, really. She has soft power, symbolically relevant, but ultimately not the be all end all. If you really want to compare this whole thing to the Catholic church, it'd be like the rulers of [Insert European nation here] going to Vatican City to study before sneaking their armies there to overthrow the church across Europe. Then after they capture Pope Leo and lock him in a basement, they declare war on surrounding countries in Europe because... before the Catholic Church was around and fucked everything up, Europe was one land with one glorious imperial ruler.
It devolves into nonsense, doesn't it? Because the structure of Edelgard's motives is nonsense.
We know she's wrong/lying about the church splitting up nations to control people, because even if Faerghus history could potentially be muddled, Rhea's newly introduced anger towards Claude and the Alliance in hopes proves she had no involvement in the Alliance's creation.
We know she's wrong/lying about the church raking in money, because the CoS doesn't take taxes. The Central Church operates on donations from nobles in the three countries. Shamir and Alois collect rewards from the Eastern Church in their paralogue, rather than take the reward from the Derdriu merchants. Hell, Mercedes confirms that the church she called home before being adopted was able to be successfully threatened with money from Random McMerchantGuy, so local churches either don't collect taxes at all, or not enough to hold socio-economic sway.
Alois may say the Eastern Church controls eastern fodlan (in JP he says they hold jurisdiction in eastern fodlan), but later in the same conversation, Alois says they don't have a standing army and Shamir says that they don't actually have a presence given they're caught between the Central Church and the Alliance lords. And the Southern Church, again, no longer exists by the time of the game.
By all measures, there is only vague similarities to Christendom when looking at the Church of Seiros in theory, and no similarities at all in practice.
So really, what was Kusakihara saying when he meant Fodlan wasn't a continent?
Well... he probably just did it for fun. He doesn't care to mention anything about Fodlan itself that would pertain to it not being a continent, aside from it being isolated enough to where the term "continent" isn't applicable because a continent would need worldwide recognition and acceptance, in accordance to post-Age of Discovery standards. And Fodlan's isolation is because its three nations are themselves extremely fucking volatile and terrible at doing anything with other countries, given what we know of Brigid, Dagda, Sreng, Duscur and Almyra. Not to excuse the other non-Duscur nations of any wrong doing on their part, since they also had a hand in invading.
But still, that and the fact that Claude in Verdant Wind is like "Um, actually looking at the Church tenets for more than 5 minutes shows that contact with the outside world isn't forbidden or sinful, guys", which should have been obvious given that Rhea let foreigners into her academy and into her personal retinue of knights; and the fact that a quest shows the Western Church hates the Central Church/Rhea because of her tolerance of foreigners... yeah, it's clear it's because each nation doesn't know how to actually treat foreign lands rather than Rhea or her church declaring non-Fodlan entities to be dangerous.
I digress. It's a similar technique to dramatic irony, where we as the readers are able to contexualize Fodlan as a continent in accordance to how we define what a "continent" is in the years 2019 and beyond. But the characters aren't meant to really... know or have awareness of those kinds of concepts.
Which naturally bumps up against, once again, the fact that there's internal contradiction in Kusakihara's statement. Yeah, of course pegasi and wyverns can fly and that's why it's easy to draw a map and stuff... does that not literally go against what you just said about isolation though? No force is shooting out every flying creature from going too far to discover what the fucking world is? There's detailed awareness of other landmasses, to the extent that there's knowlegde of other populations and even industries in these non-Fodlan places. Why then, would you try to stress to not call it a continent, before creating a world with lore that is extremely continental? "Realism" isn't an explanation nor an excuse, this is a game written by people in the past decade, striving for realism only creates issues in structure and presentation, as I just laid out.
TL;DR Kusakihara's writing is fucking weird, including when trying to intentionally make Fodlan "not a continent" before then making the rest of the world's lore extremely continent-coded.