Based on the given options and the context, the most accurate conclusion that can be drawn is:
"The expansion of the United States increased sectional tensions between the states."
This conclusion reflects the historical reality that as the United States expanded geographically, debates over the expansion of slavery into new territories and states intensified, exacerbating existing regional divisions between pro-slavery and anti-slavery factions. The other options either contain inaccuracies or misrepresent historical events.