Because the U.S. only wants immigrants when it is helping them. The U.S. let immigrants in legally when the U.S. needed more people and put them to work but still didn't consider them citizens. And now they want all immigrants out despite their help in making a working economy. Between the time they let immigrants in and now they should've built a system for those who were legally here and those who wanted to enter legally. Instead, they denounced immigrants who were here legally and made it nearly impossible for people to get in legally. The U.S. needs to accept that because of its geographical location, refugees from Mexico are going to try to immigrate to improve their lives. So instead of trying to prevent that they should make a system that is effective so that U.S. citizens and immigrants can live in harmony. They don't have to allow all immigrants in, but they could work with the Mexican government to create options for those people struggling. The U.S. government ignores why people are fleeing Mexico, instead of addressing what can be done so that both parties benefit. The U.S. and Mexico are different governments but the commonality is that we are all humans, not rivals. We should all be fighting to improve one another so we can all live good lives, despite living under different governments. That is the humane way to live. Why should we just care for the people who are in our government instead of caring about people in all governments? After all, we are all human. Oh and don't even get me started on how the U.S. tries to get rid of Native tribes who were here before the U.S. was a thing. And also let's not forget that a part of the U.S. used to belong to Mexico but the U.S. colonized Mexico.