But the wall doesn't stop these immigrants necessarily getting into the country.
Demographics of Immigrants in the United States Illegally - Illegal Immigration - ProCon.org
59% of illegal immigrants are from Mexico. That's 6.7 million. 1.17 million come from Asia. They are not going to be stopped by any wall. 1.78 are from Central and South America, I'd also assume those from South America are not going to be stopped by a wall. How did they get into the country? Probably by airplane. Walls don't stop airplane unless you build them high enough.
https://www.quora.com/How-do-illegal-immigrants-enter-the-US
"Here in Miami, many come with legitimate visas and overstay. This is a relatively well known, "
"Many that come just overstay their visas. "
"Contrary to the popular image, about 40% actually come by air, enter with student or tourist visas which they over-stay."
This is the problem. What does the wall actually do?
Fewer immigrants are entering the U.S. illegally, and that’s changed the border security debate
An article from May 2015. Yes, before Trump got in claiming to have changed everything instantly.
"Fewer immigrants are entering the U.S. illegally, and that’s changed the border security debate"
"
Monica Camacho-Perez came to the United States from Mexico as a child, crossing into Arizona with her mother in the same spot where her father made the trip before them. “Nobody stopped us,’’ Camacho-Perez, now 20, said of her 2002 journey.
Three years ago, her uncle tried to cross the border and join the family in Baltimore, where they remain illegal immigrants. He was stopped three times by the U.S. Border Patrol and jailed for 50 days.
“He doesn’t want to try anymore,” said Camacho-Perez. “Now, it’s really hard.”"
Why does the US need this wall? Well, it doesn't. So this isn't $41 billion that's going to stop the US govt from spending $54 billion. It's $41 billion that will do relatively little.