Why do these Mexican La Raza folks want this land in USA so bad?

They have plenty of wonderful land in Mexico that they make no use of, their own government is corrupt and their cities are filthy, so it makes me wonder, if they already have enough land, and a government that needs much work, and plenty of useful projects in their own country to do, why do they want this land in USA so bad? It must be for the nice cities we built right? They just want to steal our cities? If that's the plan, what happens after they kick all the white folks out and the businesses leave? The cities will have no water or power, there will be no utilities or anyone to clean up, the place will be littered, soiled, gang ridden, crime everywhere everything would be filthy and unmaintained, do they have any time table as to how long it will take to be just as filthy and run down as Mexico? And will they still want it? Or is this just a bunch of angry misguided people that really don't know what they're doing and just want to be apart of a movement?