Answer:
The expansion of US borders between 1800 and 1865 did contribute to a rise in sectionalism. As new territories were acquired, questions arose about whether they would allow or prohibit slavery. This led to debates and tensions between the North and South, which eventually led to the Civil War. Additionally, the addition of new states to the Union upset the balance of power in Congress, further fueling sectional tensions. The issue of westward expansion and the debate over whether new territories should be slave or free states became a major point of contention between the North and South, with each side advocating for their own interests. This ultimately contributed to the growing divide between the regions and the rise of sectionalism