Actually they are a waste of money.
In an effort to look like they are doing something ICE sets up checkpoints many miles from the border, in well known locations, and then trumpets the fact that they caught a couple of people who overstayed their visa, or have the wrong type of visa, or otherwise should not be here. For citizens the ICE show ends up costing you hours of sitting in a traffic jam.
In fact the same ICE agents could arrest bus loads of illegal immigrants, including ones who have committed crimes, or who are involved in smuggling people into the country, or employers who are exploiting illegal immigrants if they spent the same amount of effort and money looking where the illegal immigrants actually are.
At a recent checkpoint 90 miles from the border in very rural New Hampshire, ICE arrested 5 people on immigration crimes in 3 days of work. It would not be hard to arrest 5 people who have committed immigration crimes within an hour in many locations in New England.
Roadblocks make sense in places like Texas, California or Arizona where there are large numbers of people crossing the border. Setting up a roadblock in the middle of nowhere in New Hampshire is a waste of time and money. Those agents should be visiting dairy farms, or urban areas where illegal immigrants and traffickers are located.
My aunt who lives in New Hampshire whines all of the time about the people from Canuckistan who violate the NH border.
Just went through a Border Patrol checkpoint yesterday. It is situated thirty miles from the border at a chokepoint that is better observed and supervised than anything closer. The Patrolmen were going through a car and had the tire off. The patroldogs or sensors had picked up something. The day before they discovered 10 kilos of heroin. Just another day at the office.