The answer is: Cities
Approximately, around 80% of united states population live in the cities. This happen because most of job opportunities that exist in united states (whether it's art, technology, or manufacturing) are located in the cities.
Because of this, even people who born in rural areas start to move to inner cities in order to find jobs and sustain their living.
Nations responded to threats to their allies by mobilizing their militaries.
By the time that anyone took back the decision to go to war, it was already too late because militaries got ready so quickly. It was like lighting a fuse, it happens so fast, it is almost impossible to stop.
There was more tension between free and slave states and the Southerners feared for their safety after the raid.
The two statements that are correct are:
Europeans from many countries settled in the colonies.
People from many religions settled in the colonies.