Was the Mexican War an Exercise in American Imperialism?

I do agree with Professor Ramon Eduardo Ruiz that the Mexican War was an exercise in American Imperialism. He argued that the purpose for conquering Mexico's northern territories was because the United States waged an aggressive war against Mexico from which Mexico never recovered. The long-range effects on American foreign policy of the Mexican War were immense and the Monroe Doctrine was used to force the French ruler out of Mexico. Fearful of losing control over Texas, the Mexican government prohibited further immigration from the United States in 1830. Politicians were afraid if Texas were annexed it would upset the balance of power between the evenly divided free states and slave states that had been created in 1819 by the Missouri Compromise. Congress had voted for war 174 to 14 in the House and 30 to 2 in the Senate despite those who opposed the war. Ramon Eduardo Ruiz argued that the U.S. waged a racist and aggressive war against Mexico for the purpose of conquering what became the American southwest. Manifest Destiny was strictly and ideological rationale to provide noble motives for what were really acts of aggression against a neighboring country. President James Polk pursued the aggressive policy of a stronger nation in order to force Mexico to sell New Mexico and Texas to the United States and to recognize America's annexation of Texas without causing a war. Manifest Destiny was first territorial expansion but then later recognized as more than a mere land hunger; much more was involved. Manifest Destiny stood for democracy as Americans conceived it; to spread democracy and freedom was the goal. I think that Ramon Eduardo Ruiz had many good arguments that are listed in the above selections.