Before and during the Civil War, Americans had a lot of disagreements about how much power the federal government (like the President and Congress) and state governments (the leaders of each individual state) should have. It was kind of like a big argument about who gets to make the rules.
Some people believed that the federal government should have more power. They thought that since the country was united, there should be strong laws that applied to everyone. This side wanted to make sure that things like slavery could be controlled at the national level, so it wouldn’t vary from state to state. They worried that if each state had too much power, it could lead to unfairness.
On the other hand, many people, especially in the Southern states, believed that states should have more power and could decide for themselves what was best. This was especially true for issues like slavery. They thought that each state should be able to decide whether to allow slavery or not, without the federal government interfering. They felt that their rights as states were being threatened by the federal government trying to impose rules they didn't agree with.
These disagreements got really heated and were part of what led to the Civil War. People were arguing about states’ rights versus federal control, and in the end, it became a major fight over slavery, which many viewed as a moral issue. It was basically a huge clash between who should be in charge and who should be making the important decisions for America.