I live in a country with almost the same size of the continental USA, and we don't have even half of the number of states that America has.
Is there a reason for so many states in general, or every area of the country has his unique reason for been divided like that?
Yes. There is a reason why there are so many states,
The US spans a large amount of history. As the creation of states generally included a complete eradication of Native American societies and their political system, this will be an examination of the growth of the United States from the English system.
The English monarchy issues charters to various ventures. There were 3 unsuccessful attempts to settle Roanoke Island and then, in 1602, an unsuccessful attempt near Cape Cod. In 1606, a new charter was given out to two competing companies which set certain conditions where the winner would get sole rights to land between certain latitudes. The charters were written with a north/south boundary, but no western boundary as they did not know how far west the land would extend.
The two companies attempted their settlements over the next couple years. The northern colony failed completely and was abandoned. The southern colony survived barely in Jamestown VA and so, the Virginia Company's charter was the one confirmed.
About 12 years later, a couple other groups attempted to settle further north than the Virginia Company's charter covered. One of those groups - known as the Pilgrims - managed to survive. They were also issued their own charter with land claims extending to the west.
In 1622, there was a massive set of attacks by Native Americans against the Virginia Colony and that caused the English crown to void the Virginia Company's charter and take on the colony as a Crown colony.
At about this same time, the Dutch settled a colony along the Hudson River. Sweden also planted a colony in what is now Delaware. (Glossing over a bit here).
I will skim through the next 150 years in general terms. Spain and France settled other areas. Spain pushed into Texas, New Mexico, Arizona, California, Florida, and the coastal areas in what is now Mississippi and Alabama. France pushed in along the St Lawrence River Valley, then into the Great Lakes, then spread out from there into the states bordering the Great Lakes.
In terms of the English colonies, the Crown would periodically carve up a piece of the Virginia land charter and assign it to other people/groups for various reasons. Sometimes, a region within a colony would develop a separatist government. In any case, it was a bit of a confused mess as there were overlapping claims and jurisdiction issues from the very beginning. When they seized the Dutch colonies around New Amsterdam, they were rolled into a new charter/colony.
The important thing about this time is that Virginia had the prior and first claim to lands between the Atlantic Ocean and the Pacific Oceans from 41 degrees north to 34 degrees north. Later claims reduced that to some extent, but as of the Second Charter issued in 1609, Virginia was the big winner in terms of land claims.
Heading into the middle of the 18th Century, the English government cut back the Virginia claims based on treaties with other powers. The western borders of Virginia were scaled back to the Mississippi and Ohio. (Still glossing over how much a mess this was). The interesting thing about the Ohio River border that was established with negotiations with Native Americans is that the border was set on the Ohio side of the river, not the center of the river. Also, during the French and Indian War, the French were driven out of the Ohio River valleys and Michigan where they had settlements and trading posts. The English crown attempted to settle matters by canceling all colonial land claims in what was called the Ohio Country as Virginia and Pennsylvania disputed who had claims to that land and they didn't want the French - still in the Mississippi valley - to start arming native Americans against the british colonies..
So, overlapping land claims was a major political issue for the colonies during their fight for independence and was one of the major issues blocking a strong federal government. Virginia held most of the land west of the Allegheny mountains.
After a few years, they reached several compromises to settle land claims. A survey was hired to settle the border disputes between Pennsylvania, Delaware, Maryland and Virginia. (The Mason-Dixon line). The western border of Pennsylvania was established as a set number of miles from the ocean. (Which is why West Virginia has a northern panhandle). All states had to give up their claims for any territories west of the Ohio and the Pennsylvania/VA borders as defined by the previous agreement on survey. Virginia had to give up Kentucky County based on local opinion and support in Kentucky for an independent state. Connecticut had to give up its lands in Ohio. (The land where Cleveland is located used to be in Connecticut).
When the US purchased the Louisiana Purchase, the territory was split into smaller administrative groupings due to the radically different ways it was maintained. The Spanish and French rulers of that territory had already had an internal split where Louisiana and surrounding area fell under one internal organization and the northern ones fell under administration in St Louis. The United States Congress handled all requirements to set statehood conditions and state territories were under direct federal responsibility.
The precedence at this point was fairly well settled. Original colonies/states could not expand. Regions to the west that were geographically separated from their parent colonial claim would be admitted as a separate state. Areas acquired fell under the federal government.
The states added after the Louisiana Purchase were either by conquest, by purchase, or by settlement and they were administratively split into different shapes as needed.