Actually, it should have been secured decades ago.
Trump is the only president in my lifetime that took the issue seriously.
W did have a camera network set up on the southern border. But Obama dismantled it as soon as he took office, claiming it was too unreliable and was triggered too often by wildlife.
A little bit of AI could have fixed that. Add some Predators in the sky. There is really no reason we couldn’t intercept border crossers with or without a wall.