The Amazon river is longer than the Nile.
In the mid-1800s, the country was divided into 3 sections: North, South, and West. The North's economy was dominated by manufacturing and industry. The South's economy was primarily agriculture with a heavy focus on growing cash crops like cotton, tobacco, rice, and indigo. The West's economy was a mixture of manufacturing and agriculture. The different economies would drive wedges between the different sections and result in different societies and values.
Your 2nd and 3rd options are the correct answers. Monarchies were not quickly changed into democracies because it was much more complicated to change a government. You can't do that overnight.
For Native Americans at the time, it would have been next to impossible to understand something like the Treaty of Tordesillas. This treaty intended to partition tracts of land that the Europeans did not even know whether they existed, an action that may have looked like sheer madness and even dishonorable, for the Europeans claimed possession of lands they had not conquered by the force of their arms.Maybe, after some thought and analysis, Native Americans would have felt outraged as a man living in such a distant place, the Pope in Rome, who had no authority whatsoever for them, made the decision of handing over lands, people,wealth, etc, to two different groups of Europeans. Perhaps, other Native Americans, once they managed to understand that agreement so odd to them, might have found it laughable and it might have prompted them to challenge to take what was their own over their dead bodies.