What was the effect of the Kansas-Nebraska Act on the political landscape of the United States?

The Kansas-Nebraska Act, passed in 1854, fundamentally reshaped the political landscape of the United States by introducing the principle of popular sovereignty, which allowed the settlers of a territory to decide whether to allow slavery. This act was intended to promote the expansion of the United States westward, but it also rekindled fierce debates over the issue of slavery.

The correct answer highlights the chaotic consequences of this legislation, leading to violent confrontations known as "Bleeding Kansas." This term refers to the series of violent events and clashes between pro-slavery and anti-slavery settlers in Kansas, resulting from the contentious nature of popular sovereignty. Rather than resolving the question of slavery, the act precipitated a violent struggle, revealing how deeply divisive the issue had become.

The other options present outcomes that misrepresent the act's impact. While it did establish popular sovereignty as a principle, it did not successfully settle the issue of slavery without conflict, nor did it lead to the immediate abolition of slavery in the territories. Instead, it intensified divisions and escalated tensions that would contribute to the onset of the Civil War.