It's wild that packs of migrants can travel over desert wastelands on foot and swim across rivers to cross over the border but it's seen as impossible to get a border control officer to them when we've got access to trucks, helicopters, drones, sensors, and all the advanced technology we could ever want at our disposal.
Border patrol already has tons of access to all of the things you listed, and they can’t come close to keeping up. That’s because the task is incredibly difficult.
The solution you are describing requires tens of thousands of miles of additional access roads, hundreds of guard posts, electricity and plumbing for that, thousands of staff willing to live in remote places or commute for hours. And that’s just for the people to watch the border. Add in vehicles for all of them, thousands of sensor stations, monitoring facilities, an entire Air Force of helicopters. Realistically, you are looking at something that is going to look a lot like the logistics for the war in Afganistan. And with about the same expenses and chance of success.
It’s a bit like saying that going to the moon is as easy as sending a rocket up there.
Major cities, with far more resources than most, like Chicago, NYC, Minneapolis, and Denver are already overwhelmed to the point of crisis just from a (relatively) small number of economic migrants and asylum seekers
See: https://www.forbes.com/sites/mollybohannon/2023/08/09/nyc-ma...
https://www.nbcnews.com/news/us-news/denver-struggles-cope-4...
https://www.cnn.com/2023/10/03/politics/white-house-chicago-...
https://www.startribune.com/migrants-fill-third-of-hennepin-...
These cities can't accommodate the levels they have now. How are they, or any city, going to handle an unregulated influx of migrants orders of magnitude greater in the near future?
I understand that the task is incredibly difficult. It's also critically important. It's such a massive project that the effort needs to be started quickly. Border patrol is currently underfunded, understaffed, poorly trained, ill-equipped, and terribly managed. We're starting from a very bad position, and we don't have a lot of time. What's worse is that a large part of the country is far enough away from the problems caused by the current migrant crisis and are unaware of what climate change will mean in terms of the migration of people within the US or the influx of climate refugees so they don't see securing the border or unregulated migration as a concern. The very concept of regulating immigration has become over-politicized. The short term benefits of sustaining an easily exploitable underclass of non-citizens to be used essentially as slave labor makes keeping things they way they are now very popular with the corporations who buy off our representatives. Only after cities are overwhelmed do they start asking for the federal government to do something about the problem.
We can secure our borders, properly regulate immigration and prepare our country for what's coming now, which could allow us to accommodate as many climate refugees as we can without overwhelming our cities and further destroying our environment or we can allow ourselves to be increasingly overwhelmed by the unchecked stream of migrants coming into the country every day until we're eventually blindsided by the climate refugees and powerless to stop them from surging in uncontrolled.
The border is some of the most rugged and remote terrain on Earth. A lot (most?) of it is in country not well served by paved roads, cell service, electricity, etc. Even if you could have some sort of magic sensor network that alerted you with perfect accuracy every time someone crossed the border, the logistics of responding to every single crossing are incredibly hard. There are plenty of sections where there isn't even a road on the border.
How are you going to respond to a border crossing alert 10+ miles from the nearest agent, in terrain where it will take hours to get there by land?