Which statement was a major argument in favor of the Mexican War in 1846? Mexican forces had crossed the California border and killed hundreds of American civilians. Americans who believed in Manifest Destiny wanted to spread the American way of life. Northern abolitionists supported the war because Mexico had refused to outlaw slavery. Mexico claimed U.S. Territory in Oregon and years of talks did not settle the issue.

Americans who believed in Manifest Destiny wanted to spread the American way of life.

Explanation:

The independence of Texas strenghtened in the American public the notion that Mexico was essentially "wasting" the territories it occupied, and use the "Manifest Destiny" doctrine to justify the coming war in 1846. Essentially, Manifest Destiny proclaimed that the US had the duty to irradiate the civilization and values to the western territories, which were essentially underdeveloped under the Mexican rule, and also due to the large Native American population. As such, Manifest Destiny was part of the notion of "American exceptionalism" idea.