Massachusetts Tests for Educator Licensure (MTEL) Practice Test 2025 – Comprehensive All-in-One Preparation Guide for Exam Success

The Mexican War between the United States and Mexico was primarily caused by America's annexation of Texas, a territory that Mexico still claimed as part of its sovereign land. After Texas gained independence from Mexico in 1836, the U.S. annexed it in 1845, which Mexico viewed as an illegitimate claim to its territory. This annexation heightened tensions between the two nations, leading to military confrontations and the eventual outbreak of war in 1846.

The relationship between the U.S. and Mexico had already been strained due to issues such as border disputes and the desires of many Americans to expand the country's territory, often referred to as Manifest Destiny. The annexation of Texas was seen not just as a territorial expansion but also as a rejection of Mexico's claims, further inflaming hostilities.

In contrast, the other options do not accurately address the primary causes of the war. The Louisiana Purchase occurred in 1803, long before the conflict, while the desire to acquire land from Canada was not a factor in the war. Cultural differences in governance, although present, were not the catalyst that triggered the military action. Understanding the specific context of Texas's annexation and its implications clarifies why it was the primary cause of the Mexican War