What significant action did James Polk support that angered Mexico?

James Polk's support for the annexation of Texas was a significant action that angered Mexico due to the historical and political context surrounding Texas' independence. In 1836, Texas gained independence from Mexico and became the Republic of Texas. However, Mexico did not recognize this independence and still considered Texas a part of its territory.

When James Polk became president in 1845, he was a strong proponent of Manifest Destiny, the belief that the expansion of the United States across the American continents was both justified and inevitable. By supporting the annexation of Texas, Polk not only aimed to fulfill this belief but also sought to increase the territory of the United States. This annexation was seen by Mexico as an act of aggression, exacerbating tensions between the two nations.

The situation escalated into the Mexican-American War, which was fueled by disputes over the southern border of Texas and conflicting territorial claims. Thus, Polk's decision to support the annexation of Texas was a pivotal moment that directly contributed to the deterioration of U.S.-Mexico relations and ultimately led to military conflict.