Final answer:
Florida and Texas faced the significant obstacle of the slavery debate and the balance of power between pro-slavery and antislavery factions, complicating their path to statehood.
Step-by-step explanation:
The main obstacle that Florida and Texas faced in their efforts to become states was the contentious issue of slavery and its expansion into new territories and states of the United States. This debate highlighted a larger sectional crisis between the North and South. President Sam Houston of Texas secured a deal with President Polk, allowing Texas to join the Union in 1845 as a slave state.
Similarly, the admission of Florida also led to concern among antislavery northerners when it entered the Union as a slave state in the same year. Spain's reluctance to lose control over its territories, such as Florida, also impacted the discussions over Florida's statehood.
Moreover, the question of power and authority played a role, with ongoing conflicts about who had the right to make decisions on such critical matters. These issues of state versus federal power had been present since the ratification of the Constitution. The year 1845, with the admission of both Florida and Texas, marked a critical point as America pursued its 'Manifest Destiny' while antislavery advocates witnessed the deepening of the national divide over slavery.