This Man Is Right, Native Americans Got To Arizona First

Now the question is, who got there last: Mexicans or US-Americans?

The name of the state should give you a big clue. And the names of California, Texas, Florida, Nevada, Colorado: all Spanish names. The Mexicans were there before the gringos. Mexicans founded Los Angeles, San Francisco, San Antonio, San Diego, Sacramento and the bazillion other cities in the US with Spanish names. The US stole about one-third of Mexico, and that's about all there is to that. But if you want some additional detail, Imperialby William T Vollmann is a great place to start. The book focuses on the US-Mexico border in Imperial County, California, but also contains a lot of information about the history of the relationship between the US and Mexico generally.

Also, of course, learning a little Spanish, if you don't know any yet, would help. If you really want to know about US-Mexican politics and history.