Build a wall...what a freaking ($75b) joke.
https://www.independent.co.uk/news/world/americas/mexico-tunnel-kfc-restaurant-arizona-us-border-drug-smuggling-cartel-homeland-security-a8505761.html
The way to restrict illegal immigration is to limit employment opportunities. That guy wouldn't have been in smallville, IA, had there not been a job for him.
Sure, there are ways around employment checks - and employers that want the cheap labor are going to do the bare minimum, to ensure that they don't get in trouble (when the illegal immigrant is caught) - but that is the most effective strategy.