Manifest destiny started the dispute over the spread of slavery. Since before the Mexican-American War the states had argued about annexing new territory because of the spread of slavery. Also, this is more of a underlying factor and a personal opinion, I think that the northern population wanted to preserve the union so badly because the media had been perching manifest destiny for so long people didn't realize how bloodily and costly expansion could be. Many Americans were wrapped up in the success the US had had expanding to the west so they didn't really understand the true costs of war.
Manifest Destiny
The phrase "manifest destiny" is most often associated with the territorial expansion of the United States from 1812 to 1860. This era, from the end of the War of 1812 to the beginning of the American Civil War, has been called the "age of manifest destiny"
Chocolate good
The Mexican Cession and the annexation of Texas achieved Manifest Destiny for the US.
Because they both reunited the people of the country as well as it gave them a sense of belonging.
Manifest Destiny resulted in the population of the western US, the near extinction of Native Americans and a war with Mexico.
after the war of 1812
The Trent Incident, The St. Albans Raid, The Civil War, the Fenians, Manifest Destiny, and the end of trade
the mexican-american war
Manifest destiny led to Texas becoming a part of the United States and lead to a war with Mexico.
Because the 59=the problematic theary of bananas
the doctrine of manifest destiny