What impact did the Kansas-Nebraska Act have on the United States?

The major impact of the Kansas-Nebraska Act was that it
brought the US closer to a civil war.

The reason that it
did this was that it opened the question of slavery back up in areas where the issue had
previously already been decided.  The territories of Kansas and Nebraska were supposed
to be free territories -- slavery was not supposed to be allowed there.  But then the
Kansas-Nebraska Act reopened the issue by putting the question of slavery in those
territories up to "popular sovereignty."  This angered many in the North because they
saw it as evidence of the government caving in to the
South.

The Act also allowed for "Bleeding Kansas" to
happen.  This little war in Kansas made people on both sides upset because it involved
atrocities committed both by the pro- and anti-slavery
forces.

In these ways, the Kansas-Nebraska Act drove the
North and South farther apart and helped bring about the Civil
War.