For the most part, I would argue that the 14th Amendment was more of a reaction to the events of the post-war period, not to the 1850s. This amendment came about in large part because of the black codes that were put in place in the immediate aftermath of the Civil War. Southern leaders, some of whom had been Confederates, implemented these laws in an attempt to maintain white supremacy and white control over African Americans. This angered the Radical Republicans and helped push them to want the 14th Amendment.
However, if you need to argue that the amendment was a reaction to the 1850s, you need to cite the Dred Scott case. This was the infamous Supreme Court case in which Chief Justice Roger B. Taney declared that African Americans were not citizens, that they could not become citizens, and that they could not enjoy the privileges that came with citizenship. Since this decision had not been overturned by the Court, there was a potential need to overturn it through a constitutional amendment. The 14th Amendment can be seen as a reaction to that case.