Expansion lead to economic promise and fueled the manifest destiny but it also lead to sectional tension over slavery. The north contained a lot of abolitionists while the south was commonly pro-slavery, this increased sectional tension because each side wanted to see their ideals extended into the west.
One may also ask, was manifest destiny justified?
The term “Manifest Destiny” was, in part, an expression of a genuine ideal on the part of Americans. But it was also a justification, in that they wanted territory and needed an excuse or justification for a push into territory that they did not control.
Accordingly, why was Manifest Destiny bad?
Other historians view Manifest Destiny as an excuse to be selfish. They believe that it was an excuse Americans used to allow them to push their culture and beliefs on everyone in North America. Historians believed that expansion was for the good of the country and was the right of the people.