In my world that is set in a future Earth, there is a transcontinental country corresponding to the respective areas of the Fifth French Republic, the United-Kingdom of Great-Britain and Northern Ireland, the Kingdom of Spain, Netherlands, the Portuguese Republic, Germany, the Kingdom of Belgica, the United States of America, and most of their respective former colonies including Haiti, Canada, Ireland, Australia, New-Zealand, Jamaica, South Africa, Hispanic America, Suriname, and Brazil (the former colonies not included are most of Africa, and Republic of India).
There are ten official languages: French, English, Spanish, Dutch, Portuguese, Standard German, Russian, Hindustani, Standard Arabic, and Mandarin Chinese (the reason for the last four is because there are many immigrants that were born in Russia, South Asia, the Arabic World, and China).
But my country is a confederation. However, this is not a republic such as Switzerland, but a monarchy (or should I say a decadarchy). There are decarchs, one by official language. There are over sixty States within the confederation. The estimated human population is over 500 millions.
So, I wonder why a confederation would be a monarchy rather than a republic.