WALLING THE BORDER. In response to Mike's query below, it's worth recalling that when Goldfinger was released in 1964, there were no restrictions whatsoever on crossing the border from Mexico to the United States. People from all over Latin America were free to just wander north as they pleased and wander back again, just as they were in 1864 or at any other time from the conclusion of the Mexican War to the Immigration Act of 1965 which first restricted movement across the southern border. Consequently, it took a long time for the fact that these new restrictions were imperfectly enforced to start bothering people, and it's genuinely no surprise that we haven't managed to make our southern frontier look like the GDR border system yet.
The President's speech contained this rhetoric about how "the United States must secure its borders" which is "a basic responsibility of a sovereign nation," but in truth throughout the vast majority of our history we didn't even try and it all seemed to be fine. Indeed, around the world, genuinely "secure" borders are pretty rare and tend to reflect international military tensions rather than efforts at immigration control.
This is mainly because erecting physical blockades across borders is an unduly expensive method of restricting migration -- it's much, much, much easier to create an effective identity system combined with harsh, harsh penalties for employers who violate the rules. Most people wouldn't try to come here if it were extremely hard to get a job, and if small numbers snuck in for eccentric reasons nobody would care. The main historical use of physical boundaries is to restrict out-migration, as in Cold War-era Eastern Europe when the idea was to prevent people from leaving the Communist countries and defecting to the West. But the GOP doesn't want to take on big business, so instead you get this yearning for beefed up border security rather than draconian employer sanctions that would be cheaper to implement and more effective.
That said, I sort of think liberals might want to get behind a giant wall-building endeavor. That would be more-or-less the biggest public works project in American history, no? With the Davis-Bacon rules in effect, that's a lot of good jobs for working people.