The Treaty of Tordesillas is a bit of an historical anomaly. It makes no sense.
Why…or rather…How could Portugal and Castile, with the help of Rodrigo Borgia (Pope Alexander VI) divide the whole world between themselves?
So they draw a line on a map, running through the Atlantic from north to south. East of the line is controlled by Portugal. West of the line, by Castile.

Nowhere in the history of history have either of these countries been big/rich/powerful enough to do this. After all, Castile was historically “weak, torn by feudal wars.” And Portugal – “only a remote European backwoods.”
I’ve talked already about the division of the Great Empire. South and East came under control of the Ottomans in Constantinople. North and West was ruled by the Horde in Russia.
What if the words Castile and Portugal meant different things in the past?
Cas = Castle = Fortified City
Tile = Itil = Atil = Volga. (The Volga was named Itil/Atil in Medieval documents.)
So Castile represents the Horde.
Portu = Port = Porte. (Porte is the name given to many places in the Ottoman Empire i.e. Sublime Porte)
Gal = Golova = Glavny. (Glavny being Head or Main in Russian.)
So Portugal represents the Ottomans.
Worth a thought or two, methinks :o)