What you speak of is the ultimate goal. They will no longer be citizens of Mexico, but citizens of the NAU. That is absolutely not of benefit to you and I. But the steps taken to arrive at that end, will be accomplished with explanations of how good they are for all of us or for some significant portion of us (playing one side against another is not a new trick).
The aviation safety explanation for the new air traffic system makes sense to the average American. What explanation will they use for adding 109 million new citizens?