The term "postcolonialism" is often widely debated in literature. However, most scholars agree that a piece of literature can be viewed as postcolonialist if it depicts a country or people after colonialism has ended. However, the term can be viewed even more broadly as describing a piece of literature written about a people who are or were formerly under the rule of another people (i.e., colonialism). Although the US was never technically a colonial nation that ruled over another country's people, many argue that slavery narratives can fall under the umbrella of postcolonialism.

Beloved is about a former slave, Sethe, who is now free and living in Ohio with her daughter. The novel can be considered postcolonialist since it takes place after Sethe is freed but still contains details of how being "owned" or "ruled" by others has impacted her life.

Many parallels could be drawn between Beloved and Uncle Tom's Cabin. Perhaps the most notable parallel consists of the characters' attempts to overcome the horrors of slavery. Uncle Tom's Cabin examines life during slavery, and Beloved examines a freed slave's life post-slavery. Still, both characters struggle to overcome how slavery has impacted their mentality and way of life.

You can find a full overview of postcolonialism at the link below.