Planet England

Goes hand in hand with Expansion Pack World. You have a Magical Land that's about the size of England, since it's mostly Medieval European Fantasy. Let's call it "Magicalandia". You want to expand the world to do more stories, more locations and more Fantasy Counterpart Cultures. But what to call the world now that you can see beyond the borders of one country?

Simple! Fans are so used to the name already, that you can also call the world Magicalandia! Of course, the original country will remain the center of the fictional universe.

Thus, we have the country of Magicalandia on the planet of Magicalandia. Which is equivalent to a real-world country changing its name to "Earth" or planet "Earth" being dubbed "England", as in the trope's name.

Anime and Manga

 * Tsubasa Reservoir Chronicle has so many worlds to travel through that they just refer to each one by the name of the country or city that Syaoran et all land in (Clow, Shara, Shura, Nihon, Hashin, Acid Tokyo).

Comic Books

 * The parallel universes of the DC multiverse are referred to as "Earth-1", "Earth-2", etc.
 * Also in the DCU, the universe of Qward is named for the planet of Qward.

Literature

 * Narnia is only the name of one of many kingdoms; when Eustace tells Jill he's been to Narnia and then that he's never been to Narnia (been to the world, but not the country), Jill is understandably confused.
 * Narnia is an interesting example as the children rarely refer to their own world as "Earth", favouring "England".
 * It's an interesting example for another reason too—it lampshades a fact that makes this kind of an ironic trope: we don't have a name for our world either. It's just "the world," or "the universe." When there's only one there's no point in naming it. Uncle Andrew points this out when he's first talking to Digory about traveling to other worlds—he says he doesn't mean other planets, since those are part of our world and you could get to them without magic if you had the technology, but other universes. So maybe part of the reason the kids always talk about England instead of Earth is that Earth isn't really what they mean.
 * Dragaera is a major offender: It makes sense that there is a Dragaeran Empire with a (former) capital city of Dragaera, as this pretty much mirrors Rome. On the other hand, the universe itself is called Dragaera, and the species of its inhabitants and its language are both Dragaeran, even though there are at least two other kingdoms in the world.
 * The Riftwar Cycle almost completely averts this despite several add-ons, and actually inverts it on one occasion: We know from the beginning that the world is called Midkemia, but the main continent (Triagia) is not named for quite some time.
 * His Dark Materials takes place in a multiverse, but the issue is handled fairly well. We call our world "Will's world," since that's where Will comes from. Also, most of the characters who hear about our world only know Will. Cittagazze is really just a city, though, and the characters shouldn't be using it as the name of the entire, Spectre-haunted world.
 * They sometimes call it "The world of Cittegazze," but it's kind of a mouthful.
 * Averted in The Lord of the Rings and all related works. Middle-earth is where most of the action takes place, but the entire planet is called Arda, and it is part of Eä (the universe).
 * The Land of Oz is near such places as Ix, Ev, Mo, and Menankypoo. There's no official name for the continent on which the stories take place. The most common Fanon name is Nonestica; other proposals are Supernumquam and the Continent of Imagination.
 * Every king of Oz is named Oz, making them King Oz, of the nation of Oz, on the Continent of Oz
 * "Randland" is often used as the unofficial name for the world in the Wheel of Time, though this term (naturally) isn't used by anyone in the book. It's also used specifically for what the Aiel call "the wetlands," distinguishing it from the Aiel Wastes, the Blight and Seanchan.

Tabletop Games

 * Mostly averted with Dungeons and Dragons worlds. Although the world of Oerth (home to the Greyhawk setting) is in a crystal sphere called "Greyspace", presumably named after the City of Greyhawk.
 * Also, "Realmspace", crystal sphere of the Forgotten Realms setting, is named for a term that technically shouldn't be used by anyone who actually lives in Realmspace: "Forgotten Realms" refers to the notion that there used to be connections between Toril and Earth, which those of us living on this side have forgotten about.
 * The Ravenloft product line, and the demiplane where this setting is located, are named after a castle that most natives of that world have never even heard of. Early products had natives using "Ravenloft" to refer to the setting where they lived, though this was later retconned as a Translation Convention of an out-of-character gamers' term.
 * In Magic: The Gathering, the plane of Ravnica is named after the large city of Ravnica.

Video Games

 * The Kingdom of Hyrule within the world of Hyrule.
 * It's never incredibly consistent if Hyrule is the entire world, or just one country/continent.
 * Supposedly it's just a country of an alternate Earth, since there is also the lands of Holodrum and Labyrinia.
 * Hyrulean geography is never consistent, but it does have all the hallmarks of a country that hasn't really bothered to explore much beyond its natural borders. Hyrule's creation stories don't seem to consider the possibility that much exists beyond their home country, a characteristic of many ancient oral traditions in the real world.
 * Dialogue in Twilight Princess mentions a world beyond Hyrule, implicitly saying that it's not actually called Hyrule.
 * The Mushroom Kingdom within the Mushroom World.
 * The Kingdom of Azeroth on continent of Azeroth on the planet Azeroth. Later retconned into the Kingdom of Stormwind, the continent of the Eastern Kingdoms and the planet Azeroth, respectively, but the old names still occasionally pop up even in recent lore.
 * The southern region of the Eastern Kingdoms is still technically called "Azeroth." The manual makes a note of this in attempt to avoid confusion.
 * The country of Ivalice in the world of Ivalice.
 * Except in Final Fantasy XII, where Ivalice refers to a region made up of the main areas of the game - Rozarria, Dalmasca, Nabradia, and Archadia.
 * Daventry is an interesting example. The author of the reference materials written in-universe has a magic computer (and thus a magical Internet connection to our world). He says that he will continue to refer to the entire realm as Daventry for the reader's benefit, even though Daventry is technically only one kingdom.
 * Legacy of Kain: In all games Nosgoth is implied to be the name of the world. It contains at least two kingdoms which are never named (King Ottmar's and the Nemesis'). On the other hand, in Blood Omen 2, Nosgoth has a capitol named Meridian. Of course, Blood Omen 2 is often filed under Discontinuity or Broad Strokes anyway...
 * Might and Magic and sister Heroes of Might and Magic. Heroes of Might and Magic II introduces the name Enroth, referring to the realm the game and its prequel take place in. Cue several further iterations which interestingly take place within the kingdom of Enroth, which lies within the land of Enroth, upon the continent of Enroth, on the planet of Enroth. The name Enroth later mysteriously crops up in some spinoffs which have absolutely nothing to do with the aforementioned world. Admittedly, the Kingdom of Enroth appears to more-or-less cover the entirety of the continent of Enroth, so confusion would not be quite so common as might otherwise be the case.
 * Before Heroes III: Armageddon's Blade, which renamed the continent Antagarich, the continent of Erathia housed a kingdom of the same name.
 * Kingdom Hearts has this approach, although rather than expansion, the areas of the countries (referred to as the world) simply change.
 * The continent of Tyria on the world of Tyria. Somewhat excusable, as the original Guild Wars Tyria was planned as a complete setting in its own right, with multiple distinct kingdoms and regions. When they decided to make new sequal/expansion pack "campaigns" on new continents, the name was RetConed (along with the original Guild Wars being re-named "Prophecies campaign") to being both the continent and the world.

Web Original

 * A minor case in Lambda, not so much the level of the scale, but the frequency of its occurrence. The Five Powers are all named after their capital cities. Thus the Soleil Alliance's capital is Soleil, the Krieggarten Federation's capital is Krieggarten (even though it's made of three sovereign states), and so on. It's particularly jarring as it has the equivalent of having the Roman Republic, the United Kingdom of London, The Empire of Tokyo, etc.

Western Animation

 * My Little Pony Friendship Is Magic: Early Fanon was split as to whether Equestria was the name of the world or a country. Jossed in "Hearth's Warming Eve", which relays that the Earth, Unicorn, and Pegasus nations formed an alliance to settle in a new region they name "Equestria".

Real Life

 * Quite a number of cities have the same name (or almost the same name) as the nations or jurisdictions in which they reside, e.g. Mexico City in Mexico, Tunis in Tunisia, and New York, NY. The "naming-after" process can go in either direction.
 * In point of fact, the names of Tunisia and Algeria in their native Arabic are both exactly the same as their capitals: Tunisia in Arabic is Tūnis (as for is Tunis the city), while both Algeria and Algiers are Al-Jazā'ir. Kuwait is the same way, but since it's basically a city-state, that's not this trope.
 * In fact, the name of just about every country in the world derives from some specific area, geographical feature, or tribe within that country or its distant past. For example, "France" from the Franks and "India" from the Sindhu River. After all, whoever got the privilege of naming a sufficiently large area wouldn't have had a bird's-eye view informing them of the entire area's qualities. Plus, many countries/regions result from the fusion of several smaller places, eg, The Roman Empire is named after its capital city of Rome.