• The Civil War firmly established the concept of "perpetual union" only hinted at in the founding documents
• The Civil War ended slavery, which was a hot-button issue when the nation was founded
• When the Civil War broke out, the memory of the Revolution was still quite fresh--it was the war of their grandfathers. Both sides thought they were sustaining the dreams of the Revolution
• The Civil War greatly expanded the power of the federal government (first income tax, for one example), which was weak in the aftermath of the Revolution
• In the Revolution, the soldiers were not well cared for. They were poorly fed, poorly documented, and poorly pensioned. This led to aftershock rebellions after the Revolution, but during and after the Civil War the soldiers were better cared for through the introduction of a variety of new bureaucracies

The historians here generally don't like writing papers for others, but I respect the fact that you've been searching all night and it would be a hard question for a new student of the subject to answer. Hope this helps!