I wish I could share your optimism. Maybe that's been the experience in Texas but in L.A. the spanish speakers intend to make this state a culturally "spanish" state. They are not just lazy, they are adamant against assimiliating into the American culture.
I worked two blocks from Pico and Union back before the Rodney King riots. There was an appliance store in that building which did business entirely in Spanish. This is not just spanish in the home, it is all spanish all the time , everywhere. (BTW, the looting and arson around my office building was done not by blacks protesting the King beating but by hispanic men, women, and children looking for freebies.) That store now owns the entire building and the last time I drove by, everything is still in spanish.
"[T]his is [not] the end of the world ..."
No, of course this is not the end of the world. It is just the end of America culturally. America will go on with a new culture. History will look back and assign actions it takes to be "American" but it will bear little relation to what our nation was when it was founded, and instead will have transformed into a very different society.