The Mexican-American War was a conflict between the United States and Mexico from 1846 to 1848. The war began with an American invasion of northern Mexico, following disputes over claims by U.S. citizens on land in Texas that had been annexed by the United States in December 1845. During the war, US forces captured much of northern Mexico, including its capital city, as well as parts of California and New Mexico before it ended with the Treaty of Guadalupe Hidalgo in February 1848. The treaty ceded large tracts of territory to the United States for $15 million and recognized Texas' independence from Mexico.

In addition to territorial losses, many Mexicans were displaced during this period due to violence or fear associated with their nationality. Some even migrated northward into what is now Arizona and Colorado after their homes were destroyed or abandoned during battles fought throughout modern-day California and New Mexico territories such as San Pasqual (1846) and Buena Vista (1847). As a result, these areas became populated by more Americans than ever before, leading them further away from Spanish influence. This simultaneously strengthened Anglo control over new lands acquired through conquest or purchase – like Alaska – plus those already belonging to America prior to hostilities breaking out between the two nations along America's southern border region, known today as "the Southwest", which includes present-day states like Nevada, Utah, Colorado, Wyoming, Kansas, etc.

The consequences of this long-forgotten but nevertheless important episode in history have impacted North American politics up until current times – especially concerning issues related to immigration reform, where language used against certain groups perceived as "foreigners" continues being deployed without any real understanding about why they have arrived here nor respect towards people who are trying to make better lives for themselves despite difficult circumstances beyond their control. It is worth noting how the far-reaching effects still felt today can be traced back all the way to when the USA declared itself an independent nation in 1776 after having waged the Revolutionary War against Great Britain a few years earlier.