In the US, Mexico
First, it is a myth that all immigrants are Mexicans, and it is also a myth that the US is being overrun with illegal Mexican immigrants. While many illegal immigrants are indeed from Mexico, many are not. (And it should also be noted that many immigrants from Mexico are legal, and have every right to be here.) Studies have shown that there are illegal immigrants from numerous countries, including Ireland and China, who come to the US and either overstay their visa unintentionally or decide they don't want to leave, even when they are supposed to. As for Mexicans, many do in fact go back to Mexico. But others stay, and in some cases, they live in the shadows for years, working at jobs many Americans don't want to do.
Supposedly, to prevent Mexican illegal immigrants from reaching US soil.
Yes, there are many illegal immigrants who lived and worked in the United States and no official record of their whereabouts are being held.
Supposedly, to keep illegal immigrants, criminals and terrorists out of the United States.
I think it's New Mexico?
about one quarter
About 36 million
You mean enforced? No. It is as porous as it can be. Drugs, weapons and illegal immigrants cross it everyday on both sides.
The US needs illegal immigrants. Many of these people are willing to do jobs that legal US citizens will not. They are extremely hardworking people and are just looking for a better life for their families.
An illegal immigrant to the US is, by definition, a person who has entered the country in a manner which violates US immigration law. That is the distinction between legal immigrants and illegal immigrants. So yes, they get deported.
23 (America)