Question

What caused America to enter a new era as a republic?

Answer 1

America was sick of monarchies. They were inspired by works of people such as Locke and Rousseau who spoke that people give power to rulers and not god or anything similar. That's why they opted for a democratic republic where rulers would be chosen and prevented from tyranny by law.

Answer 2

While there are indeed a plethora of reasons that led to it, the Revolutionary War and the resulting aftermath -- the United States winning and gaining independence -- led to the creation of the early republic which started with the Constitutional Convention of 1787, where America had to tackle constructing a governmental system that wasn't centralized in one branch, but instead allowed for multiple branches with elected representatives who could check the powers of the other branches and elected officials.