Final answer:
The Declaration of Independence is the document that formally freed American colonists from British governance, written by Thomas Jefferson and grounding itself in Enlightenment principles and republicanism after the war for independence.
Step-by-step explanation:
The declaration that formally freed the American colonists from British governance is the Declaration of Independence. Crafted by Thomas Jefferson, this pivotal document based on the Enlightenment principles and was signed in 1776. It not only articulated the colonies' reasons for rebellion but also established the right to life, liberty, and the pursuit of happiness, echoing the social contract theory of John Locke. The Declaration of Independence was a landmark in asserting the right of the people in American colonies to self-governance and ultimately led to the creation of a new nation founded on democratic principles.
Following the war for independence, the American revolutionaries embraced republicanism as their form of government. This system is based on the notion that the citizens hold public power and elect representatives to govern on their behalf, rather than continuing with a monarchy or other forms of government. The enduring significance of the Declaration of Independence is evident as it inspired subsequent struggles for independence and shaped the development of the United States' federal system. Moreover, this historic move towards independence culminated in signing the Treaty of Paris in 1783, formally ending the war with Britain.