Evidence to refute the claim, The Mexican American War, fought between 1846 and 1848, was a pivotal event in shaping American history as it not only expanded the territorial boundaries of the United States, but also exposed the deep-rooted cultural, political, and racial tensions between Mexico and America, ultimately leading to significant consequences for both nations.

1. Limited impact on shaping American history: While the Mexican American War did expand the territorial boundaries of the United States, many argue that it did not have a significant impact on shaping American history. The United States had already been expanding westward through the Louisiana Purchase in 1803 and the annexation of Texas in 1845. The war only added relatively small territories to the United States, such as California, New Mexico, and parts of Arizona, Nevada, Utah, Colorado, and Wyoming, which were already sparsely populated.

2. Cultural tensions existed prior to the war: Cultural tensions between Mexico and America existed long before the Mexican American War. The two nations had differing languages, religious beliefs, and political systems even before the war started. Mexican Americans, who resided in the areas that became part of the United States after the war, had already been living alongside Anglo-Americans in these regions, and cultural tensions between them were not solely a consequence of the war.

3. Political and racial tensions existed within the United States: The notion that the Mexican American War exposed deep-rooted political and racial tensions between Mexico and America overlooks the fact that these tensions were present within the United States itself. Even before the war, debates over slavery and its expansionist implications had been dividing the nation along political and racial lines. The war itself was a result of these tensions, as the annexation of Texas and the desire for further expansion sparked conflicts with Mexico.

4. Economic factors played a significant role: The claim fails to acknowledge the economic motives behind the war. The United States sought to acquire Mexican territories in order to expand its economic influence and access to valuable resources, such as gold in California. This economic motivation was a driving force behind the war, overshadowing cultural or racial tensions between the two nations.

5. Limited consequences for Mexico: While the war had significant consequences for the United States, its effects on Mexico were more limited. Mexico lost about half of its national territory, but it still retained a substantial portion of its land. Additionally, Mexico had already been facing internal unrest and political instability even before the war, and attributing all the consequences solely to the conflict would oversimplify the complex socio-political context of the time.

Overall, while the Mexican American War did have important consequences, such as expanding the territorial boundaries of the United States, it is more accurate to consider the war as a continuation of existing geopolitical trends and tensions, rather than a pivotal event that fundamentally shaped American history or solely exposed cultural, political, and racial tensions between the two nations.