Mexico, including what is now the SW US, was part of New Spain for 300 years. The Mexicans fought a revolution to win their independence from Spain, ending in Mexico's victory in 1821.
In 1836, Texas won its independence from Mexico, though Mexico never recognized it as such. In 1845, Texas agreed to become part of the United States, which triggered the Mexican-American war in 1846, which the US won in 1848.
Mexico agreed to cede what is now the American SW to the US, while the US agreed to pay 15 million dollars (plus another 3 million owed to Americans by Mexico) to Mexico.
The people who find America's annexation of the former north of Mexico have no leg to stand on. If they think revolution is illegitimate, then so was theirs, and the entire country of Mexico should go back to Spain.
If they think winning land by armed conflict is illegitimate, then again, Mexico should go back to Spain, because armed conflict was how they got it.
If the issue is their lack of recognition of Texas as an independent state prior to its annexation by the US... well, you can refuse to recognize that fire is hot, but it doesn't change anything either.
When the Mexicans withdrew to south of the Rio Grande and left the land under Texian control, that meant Texas was independent.
Spain had the SW US states for 300 years. Mexico had the region for 27 years. The US has had it for 170 years. Why, somehow, is the 27 year span more valid than the others?
This comment was left by Silvestris at Breitbart - Read more of Silvestris's comments at https://disqus.com/by/disqus_WTIJVjj1y2/