there are still Bourbon Restorationists in France. I believe they have a political party.
On a more ancient note, after the last traces of the Western Roman Empire dissolved in the 470's, the dream of it did not die. Almost a hundred years later, Justinian was still trying to recreate a united Roman Empire, and he nearly did. In the end, though he mostly helped make things in the west worst than they already were. Indeed creating the office of Holy Roman Emperor to placate Charlemagne almost 300 years after Romulus-Augustus was sill some glimmer of the idea that had been Rome, though it was not at all a return to some forgotten status quo. It can be a fringe idea, but it can also be an idea held onto by people who have a vague consciousness of better days behind them.
The Holy Empire was not the Roman Empire, it was a new state with laws and administration different from what the Roman Empire was and did not include the entire Western Empire and also had new territories.
what I'm saying is that from what we see in the show there is no longer a state called the federation, only isolated groups that continue to believe in the reconstruction of something that ceased to exist.
states die and what comes next is no longer the same