A. Colonists Became significantly less involved in politics
The Andes, Alps, and Rocky Mountains are some examples. It's usually where the snow line of mountains begins.
Brutus' vision of republic is outdated. Diversity of opinion is vital for a republic.
It's necessary for a republic to have people who represent all kinds of people in it. Different classes live different lives, and it's hard for a person who belongs to one class to be aware of the needs, manners, interests of people from a different class. For this reason, diversity is a very important part of a republic.
A republic should <em>NOT</em> be made up of a small group of people who think in a similar way. On the contrary, it <em>should</em> be made up of people from different backgrounds, in order to better represent its people.