Corvus, I will admit to never having read the Treaty of Guadalupe Hildalgo, though what you say does not surprise me. I appreciate you sharing some of what you know and your perspective.
I am fine with folks speaking Spanish or any other native language at home or with their compatriots. My mother’s parents spoke French at home when she was young. I also think retaining certain cultural celebrations and traditions adds flavor to the larger society. What I wouldn’t give for my grandmother’s tourtiere during the Christmas holidays. What I am not fine with is any group that comes to the US without the intent to otherwise assimilate into an English speaking America whose cultural heritage is primarily European. In practical terms I would hope that the folks from Mexico/Central America/South America would recognize that what evolved out of the British colonies in what is now the US and Canada worked out far better than the model Spain and Portugal set in motion with their colonies to the South. I don’t want the Southwest US to become North Mexico because Mexico is a failed State plain and simple. All that said however, my guess is that the La Raza folks will lose out and that the Hispanic community will eventually assimilate with a new “normal” arising.
Coming back to the original group this thread was talking about, the Muslims are the real problem the US faces, not the folks from Mexico and points South. They are still few in numbers but their influence is growing far larger, and they are utterly incompatible with our culture. Any group that will not recognize the Constitution as the highest law of the land should not be here. There is no place for Sharia law in Western society.