The battle over the fate of the Africans in Amistad is a microcosm of the growing sectional conflict in the US in two ways. First, the battle shows how there are a diversity of views on slavery, even within the North. Second, the battle shows how the North and the South were each coming to think that the other side held too much power.
This movie is set in 1841. In that year, there was already tension between the North and the South over slavery, but the tension was not as high as it would be a few years later, following the Mexican-American War. For example, Nat Turner’s rebellion had happened and the fight over the Congressional gag rule on discussions of slavery had also occurred. This shows that slavery was already an issue between the two sections of the country.
The first thing that the events of the movie show is that the North was not a monolithic entity when it came to attitudes about slavery. Northerners did not typically support slavery, but neither were they usually abolitionists. Most of them simply did not want slavery to spread. Therefore, we see (for example), William Holabird, who is from Connecticut, siding with John Forsyth of Georgia on the issue of whether the Africans should be freed. We also have President Van Buren of New York being unhappy with the outcome of the case at the appellate levels even though those courts found in favor of the Africans. In short, we see that attitudes about slavery are more complicated than we often believe.
Second, we see that both sides have reason to believe that the federal government favors the other section. We see the Secretary of State of the federal government actively supporting the pro-slavery position. We see the President supporting this position to some degree as well. At the same time, we have the Supreme Court of the United States ruling against the pro-slavery position. This means that both sides in the conflict end up suspicious of the federal government. Each side thinks the federal government is in the pocket of the other side.
In both these ways, the events of this film can be seen as a microcosm of the growing discord between North and South.