It is a very difficult question to answer but I would dare to say that to the US Government, money and 'big business' have top priority.
When illegal immigrants arrive to US' soil, they apply for jobs most other people think as 'degrading to their dignity as human beings'. Also as they are illegal, they are paid with much lower wages than any American citizen. This of course, proves to be a good deal to many employers, for they can find a sizable pool of cheap workers and if the case might be, they can bully their employees to 'work more for less, because Juanito will work the same as you for half the pay'.
On the other hand, the US southwest used to belong to Mexico, so many people consider it -- specially right-wing conservatives -- as part of the reconquista. However, even if someday people of Mexican origin become a majority, it is very doubtful they all agree to split-up and join Mexico again.
Long story short, they are looking for the "American dream". As many of them are illegally working in the United States, many unscrupulous employers give them jobs for smaller wages than otherwise Americans would work for; also most of them work in fields and areas that many Americans never wanted to begin with, such as agriculture and ranching, construction and cleaning services.
The US did take a part of Mexico which is now Texas
they fought over land, mostly what is now the southern united states including texas, new mexico , and california
The US did take a part of Mexico which is now Texas
Texas bordor Mexico and that's where the take over took place with Napolian Barnapas in 1812. The fight for the territory of Louisiana purchase and Mexico protecting its territory.
about how long would it take to walk from east Texas coast to Mexico citey
Mexico, Mexico, Mexico Mexico,Mexico, Mexico
The Battle of the Alamo, was part of the struggle for Texans to take back Texas from Mexico, and create an independent American State of Texas.
about how long would it take to walk from east Texas coast to Mexico citey
To summarize, California, Nevada, Utah, Texas and parts of Colorado, Arizona, New Mexico, and Wyoming were part of Mexico and now belong to the US.
Texas (more specifically, the annexation of Texas into the Union).
Texas under Spain Texas under France Texas under Mexico
because they wanted to