In much of the United States, victory and the acquisition of new land brought a surge of patriotism. Victory seemed to fulfill Democrats' belief in their country's Manifest Destiny. Although the Whigs had opposed the war, they made Zachary Taylor their presidential candidate in the election of 1848, praising his military performance while muting their criticism of the war. Many of the military leaders on both sides of the American Civil War of 1861–1865 had trained at the U.S. Military Academy at West Point and had fought as junior officers in Mexico.

For Mexico, the war had remained a painful historical event for the country, losing territory and highlighting the domestic political conflicts that were to continue for another 20 years. The Reform War between liberals and conservatives in 1857 was followed by the Second French Intervention, which set up the Second Mexican Empire. The war caused Mexico to enter "a period of self-examination ... as its leaders sought to identify and address the reasons that had led to such a debacle." In the immediate aftermath of the war, a group of Mexican writers including Ignacio Ramírez, Guillermo Prieto, José María Iglesias, and Francisco Urquidi compiled a self-serving assessment of the reasons for the war and Mexico's defeat, edited by Mexican army officer Ramón Alcaraz. Denying that Mexican claims to Texas had anything to do with the war, they instead wrote that for "the true origin of the war, it is sufficient to say that the insatiable ambition of the United States, favored by our weakness, caused it.