Respuesta :

The Mexican/American War was an armed conflict between the United States and Mexico that took place in 1846–1848.  However, Mexico refused to accept these as valid, claiming the border was the Nueces River. U.S. President James Polk endorsed the Rio Grande boundary, which incited a dispute with Mexico.

I hope this helped:)
borders of Texas caused a dispute that led to the Mexican American war. via apex us history