Evidence to refute this 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.

One piece of evidence that refutes the claim that the Mexican American War was a pivotal event in shaping American history is the fact that the war did not significantly expand the territorial boundaries of the United States in the long run. While the war did result in the acquisition of vast territories including California, Nevada, Utah, Arizona, New Mexico, and parts of Colorado and Wyoming, these territories were already largely unsettled and sparsely populated at the time. The original plan of expanding further into Mexico was abandoned due to political and logistical challenges, and the border between the two nations was reaffirmed with the Treaty of Guadalupe Hidalgo.

Additionally, the claim overstates the deep-rooted cultural, political, and racial tensions between Mexico and America. While there were certainly tensions between the two nations, it is important to note that these tensions were not unique to the Mexican American War. The history of relations between neighboring countries often involves some degree of tension and conflicts over borders, resources, and political ideologies. The Mexican American War was just one chapter in a long history of interactions between these two nations.

Furthermore, the claim does not adequately address the complexities of the consequences for both nations. While the war did have consequences for Mexico, such as the loss of territories and the exacerbation of internal political turmoil, it is debatable whether these consequences were solely a result of the war. Mexico was already facing a number of challenges, including political instability and economic struggles, which predated the war.

In conclusion, while the Mexican American War was undoubtedly a significant event in the history of both Mexico and the United States, it is misleading to claim that it was a pivotal event in shaping American history. The war did not extensively expand American territorial boundaries, and the claim overstates the unique nature of cultural, political, and racial tensions between Mexico and America. Additionally, the consequences of the war for both nations were more complex than what can be solely attributed to the conflict itself.