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.
The Kansas-Nebraska Act was a controversial bill that led to further divisions between North and South. The bill allowed for settlers within a territory to make decisions about whether they wanted to allow slavery or not. This change was buried within a bill that was about new territories, the future Transcontinental Railroad, and farmland.
The bill was introduced in Congress by Stephen A. Douglas. The primary purpose of the bill was to officially establish a new territory in the midwest. Due to the location of this territory, it should have been a free territory according to the terms of the Missouri Compromise. Wanting to gain the support of Southerners in Congress, Douglas proposed that the territory be split into two, Kansas and Nebraska. This also led him to suggest that the settlers in the more southern of the two territories decide if they wanted to allow slavery or not. This idea was called "popular sovereignty." Kansas was established as a slave territory. Northern opposition led to tensions. Abolitionists had opposed the bill. Slave owning settlers moved to Kansas. Abolitionists also moved to Kansas in opposition. An official legislature was established, and in opposition an unofficial one was also established in a different town. Abolitionist John Brown murdered farmers who were proslavery, and eventually fighting broke out between abolitionists and those who believed in slavery. It was a war on a small scale. This time was later referred to as "Bleeding Kansas." Tensions due to these events contributed to the rift between Southern and Northern states, which eventually led to the Civil War.
Kansas-Nebraska Act of 1854 repealed the Missouri Compromise of 1820. It applied the principle of popular sovereignty to the territories. It permitted the expansion of slavery beyond the Southern states. It also sparked the formation of the Republican party. This Act would be one of the causes of the Bleeding Kansas and the Civil War.