Besides the likelihood of war with Mexico why did annexation take so long?

1. Polk's desire for a negotiated settlement: While Polk was committed to the annexation of Texas, he initially attempted to negotiate a deal with Mexico to avoid a war. He sent diplomats to Mexico to try to secure a sale or cession of Texas, but the Mexican government was unwilling to relinquish control of the territory. Mexico viewed Texas as a rebellious province and refused to recognize its independence or cede it to the United States. Furthermore, Mexico had recently been defeated by France in the Pastry War and was in no position to militarily resist annexation.

2. Opposition within the United States: Despite the overwhelming support for annexation among Southerners and Western expansionists, there was significant opposition to the annexation of Texas within the United States. Many Northerners were opposed due to the potential impact of annexation on the balance of power between the free and slave states. The addition of Texas as a slave state would have given the South additional power in Congress and would have likely increased tensions over slavery.

3. Treaty ratification process: Once the annexation treaty was negotiated between the United States and Texas, it had to go through the ratification process, which required the approval of two-thirds of the Senate. The treaty faced significant opposition from Northern Senators, who feared the potential impact of annexation on the balance of power between the North and the South, as well as the likelihood of war with Mexico. The treaty was ultimately approved by the Senate in late December 1845, but it took several months for the process to be completed.