Final answer:
During the Texas annexation debate, President Tyler and Americans feared that the move would lead to conflict with Mexico, which it did, resulting in the Mexican-American War. The issue of slavery in new territories was also a major concern as it threatened to disrupt the sectional balance and intensify national divisions. The concept of 'Manifest Destiny' and the rush of settlers to Texas added to tensions and indicated emerging pro-slavery and expansionist attitudes.
Step-by-step explanation:
The question at hand explores what President Tyler and Americans feared about Texas during the annexation debate. The annexation of Texas to the United States was a contentious issue during the 1840s, with concerns centered on several fronts. One fear was that the annexation would lead to increased conflicts with Mexico, as it would be seen as an American encroachment on Mexican territories. This concern was valid, as the annexation eventually became a causal factor in the Mexican-American War.
Additionally, the topic of slavery in new territories was another significant fear. The annexation of Texas, a region where slavery was practiced, threatened to reignite national debates about the extension of slavery into newly acquired territories. This issue stirred apprehensions within the northern states and brought forth a sectional divide, as the admission of more slave states could disrupt the balance of power between free and slave states.
Finally, emergent American attitudes manifested in the concept of 'Manifest Destiny,' the belief in the inevitable expansion of the United States. This ethos underpinned expectations of both pro-slavery expansionists and those seeking new opportunities in the fertile lands of Texas. Despite official hesitance, the U.S. annexation of Texas represented not only the culmination of expansionist dreams but also set the stage for the broader sectional crisis surrounding slavery.