5 Roman successor states that think of themselves as Romans (or xxx-Roman like the Greco-Roman Byzantines?) okay…
The POD is the survival of the Western Roman Empire, possibly under a Goth as the Emperor. Both Empires are Christian. Islam’s spread in the west is kept in check by the Byzantines, who manage to keep a hold of their possessions in Africa and Southern Spain.
As is the way with these sorts of timelines, things progress faster, such as the discovery and exploitation of the Americas.
Both West and East carve out lands in the Americas, fighting the natives and each other in the process. By the middle of the 14th Century, the West is victorious, having pushed the Byzantines out of most of the Borealis; their few remaining possessions are a few fortress islands, the trading port of New Constantine, and the penal colony on the eastern coast of Australis where Turks are being resettled.
In 1337 AD, this all falls apart with the arrival of the plague in Europe and the beginning of the Great Plague. When the Western Emperor dies, either due to the plague or overdose of steel, General Maximus Flavius seizes power, and the Western Empire descends into Civil War. The Emperors son Alexander is in the West Roman colony of Mexico, and when news of the chaos reaches the New World, he has himself crowned Emperor of Rome Outer-Mare, Rome across the Sea. The colonies of Maiya and Mosquitos join Mexico as parts of Rome Outer-Mare, and Emperor Alexander invites the other Western colonies to join the ‘true Roman Empire’.
The Northern colonies don’t join Rome Outer-Mare, instead the mainland colonies form Nova Aquitana, a state independent of both West and Outer-Mare Rome.
Ionia Outer-Mare (its name betraying its Byzantine heritage) remains loyal to Western Rome, as does Thule (The Northmen outpost in the New World under Western protectorate) and Nova Tuscany.
The other Western Roman colonies rebel. Nova Britannia declares her independence, as does the island of Nova Amorica.
Nova Amorica had been the heartland of Western Roman presence in the New World, the oldest colony, having been settled for four hundred years. When news of the death of the Emperor reached them, they chose a different course. Established primarily as a independent republic under the current governor, that regime is overthrown, and replaced with the Republic government. The idea behind the Republic is thus: The Republic is the original Roman form of government, one that has been destroyed by the rule of Emperors for over a thousand years. They are the true Romans.
The Byzantine holdings in the New World on the other hand are rather stable. The only one that slips out of Byzantines orbit is the Turkish penal colony, where Turks overthrew the minor garrison and declared themselves the Emirate of Arslan.
So what do we have here?
How many Roman successor states?
1. Western Roman Empire (Civil War)
2. Byzantine Empire
3. Rome Outer-Mare
4. The Republic
5. Nova Aquitinia