Why did the mexican-american war ultimately divide the american public and provoke political dissension?

Because it started an argument over making the new territories slave or free states causing even more tension between the North and the South

The transcontinental railroad provided a means of fast transportation. it cut a 6 month trip into 6 days, created jobs for many people and encouraged immigration. the homestead act played a huge role in western expansion; it allowed settlers to begin a fresh start, and gave them land in exchange for their residence for up to five years and a small fee.