Final answer:
The defining characteristic of the Early Republic was the renewed sense of nationalism following the War of 1812, marking a period of increased unity and identity that distinguished the nation from Great Britain.
Step-by-step explanation:
A defining characteristic of the Early Republic was a renewed sense of nationalism following the War of 1812. This period, often referred to as the Era of Good Feelings, saw a significant surge in national pride and unity. The war confirmed the United States as a sovereign nation, separate from Great Britain, and propelled the country to focus on westward expansion. During the Early Republic, there was no cession of territory to Great Britain, so option A is incorrect. Mercantilism and tensions over British economic policies were precursors to this period, which inform options C and D, but they are not defining characteristics of the Early Republic itself. Thus, the correct answer is B: There was a renewed sense of nationalism following the War of 1812.