Why was it hard to annex Texas?

Answer 1

This is because Texas was not technically American soil to begin with. It was originally Mexican territory until a vast number of Anglo-Saxon migrants began to inhabit the land, much to the displeasure of the Mexican government. The tension between the settlers and the Mexican government soon broke out into the Mexican-American War (which many US Presidents including Andrew Jackson and Zachary Taylor served in) and the eventual independence of Mexico.

The main problem, however, was not the struggle for independence, but rather the dispute over slavery. Under the Missouri Compromise, states under the 36°30' parallel could choose whether or not to allow slavery. The South was willing to admit another slave state: Texas. The North was not. At the same time, there was an ensuing struggle in Canada for the boundary of Oregon. Half of the nation was concerned with Oregon, and the other half was concerned with Texas. The topics were so debated that they became the focal point of the 1844 election; the two parties ran on opposing platforms, with James K. Polk for the annexation of Texas, and Henry Clay opposing the annexation of Texas. James K. Polk won with 170 electoral votes to Henry Clay's 105, and in 1845, Texas was annexed and became the 28th state in the union.