Final answer:
The annexation of Texas had pros such as security and alignment with the westward expansion of the US, but cons like potential war with Mexico, exacerbating the national slavery debate, and assuming Texas's debt.
Step-by-step explanation:
The annexation of Texas into the United States had both advantages and disadvantages. Sam Houston, the first president of the Lone Star Republic, had dreamed of Texas joining the US, aligning with many settlers who sought to expand westward. The pros of annexation included protection from any further Mexican attempts to reclaim Texas, recognition from other nations, and the continuation of slavery which was critical to many Texans, including prominent figures like William B. Travis and James Bowie. However, it also had significant cons. The potential for war with Mexico was a serious threat, which did materialize as the Mexican-American War. The debates over the admission of Texas as a slave state further intensified the sectional crisis over slavery, particularly when balanced against the admission of free states like California. Additionally, the annexation meant that the federal government would absorb Texas's debt and reduce its territory by asking it to cede land to New Mexico.
Texas ultimately did join the Union in 1845, but this move came at the cost of exacerbating national divisions and leading directly to the Mexican-American War. Whilst some Texans had always dreamed of being part of the United States, hoping it would provide economic and political stability, the reality of its incorporation brought forth a complex mix of nationalistic ambitions, the drive for territorial expansion, and the issue of slavery.