Newsflash to Mexico; we didn't STEAL anything. Texas rebelled against a revolutionary government which suppressed the original constitution under which the Texans were happily living, and the U.S. paid
$15 million them for Texas as part of the Treaty of Guadalupe Hidalgo. That was when fifteen million was real money (we paid that much for the Louisiana Territory.) We purchased the deeper southwest from Mexico as part of the Gadsden Purchase, proving Mexico had no interest in this land anyway I should also mention that Mexico only laid claim to that area because the Spanish had first claimed it, and they had few settlements and very little defensive capabilities in Texas or the Southwest. California rebelled against Mexican rule too and was an independent Republic for a short time. And Texas and California weren't the only places to rebel; Coahuila did, for instance and was destroyed by Santa Ana. There was also a Republic of the Rio Grande' on both sides of the river that would be destroyed by the Napoleon of the West as well. Mexico lost those territories because they couldn't get their act together and keep them. America in no way "stole" those territories. Also, a good chunk of Texas was supposed to be ours anyway; we bought it as part of the Louisiana purchase. Mexico claimed it and so we didn't argue at the time. But they stole it from us. We got it back.
(BTW I'm always interested in the small countries that would incorporate into the U.S. or attempt to splinter off from her. These include the Republic of West Florida which existed for ninety days after rebelling successfully against Spain and included the gulf coast up to Louisiana. It also included the Republic of the Rio Grande' and Texas and California and Hawaii. And of course there was the Confederated States of America. I find West Florida interesting; after kicking the Spanish out with the help of Jean Lafeet, the pirate, they applied for annexation but were given no answer so established their own government. After three months James Mdison decided to take the bull by the horns and just annexed it on his own, sending troops. The government there decided to fight it out and sent their own forces to oppose the Americans but upon seeing a strong, disciplined military thought better of it and so didn't fight and thus became the states of Mississippi, Florida, Alabama, and Louisiana. The Bonny Blue Flag was their flag, and Texas stole the lone star from them.)
At any rate Mexican claims they were robbed are horsepoop. If they didn't want to lose that land they should have settled it themselves and developed it, and they shouldn't have picked a fight with us. It was the threat of Mexican troops massing along the southern border that led to the Mexican War in the first place.