Why did Mexico break diplomatic relations with the United States in 1845?

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Mexico severed diplomatic relations with the United States in 1845 primarily because the United States annexed the Republic of Texas that same year.12

Although Texas had secured its independence from Mexico in 1836, Mexico had refused to recognize it as a sovereign nation. Consequently, the Mexican government viewed the U.S. annexation of Texas as an aggressive act, which prompted the immediate rupture in diplomatic ties.2