Final answer:
As the nation expanded westward, elements of American society such as the plantation system, slavery, and the concept of manifest destiny were also extended into new territories, along with settlers, laws, and government systems.
Step-by-step explanation:
As the nation expanded west, not only did the physical territory of the United States grow, but various elements of American society also expanded into the new regions. This included the spread of the plantation system and slavery, largely into areas that would become the southern states.
Additionally, with western expansion, manifest destiny, the idea that Americans were destined to spread across the continent, became a guiding principle for the country's growth. Other aspects that spread with westward expansion included laws, government systems, European-American settlers, and in many cases, conflicts with Native Americans who already inhabited the land.