There's a partial wall that got halted, I don't think the majority were immigrants that built it to a certain point. Though not saying there wasn't any, people do get work visas to work in America. There's all kinds of programs to help people work, go to school and move to America.
Alot of folks don't want to go that route because they are doing something illegal like drug trafficking that crosses the border. Resently I've read 20o people are dying a die from the uptake in drug trafficking because of the open border policy that's not the policy according to the current administration.