We have a very difficult legal immigration process. That adds desperation for people to try to get in illegally. We also have a country (Mexico) that struggles to contain its cartels, just across the border. The cartels have ridiculous amount of funding, resources, firepower, etc. In many ways rivaling or greater than Mexico's own government and military. Stopping them isn't easy. The border is extremely long as well. That does not mean we have "open borders," far from it. The Biden administration is still stopping lots of people outside of the border under [EDIT: programs similar to] the Trump administration's "remain in Mexico" policy. [1] [2] Getting in is dangerous, and CBP/DHS detains many, many people on the way in. The fact that there have been more apprehensions at the border than ever means enforcement is doing its job more than ever before. It's just not an "open border", plain facts.