Illegal immigration

That is when people without legal permission from a country cross the border and lives there illegally.

American illegal immigration problem

This has become a major problem in the United States, because the number of Mexicans living in the U.S. is becoming bigger and bigger. Illegal immigrants don't pay taxes and they use many services. They they don't learn the language. This reduces services for Americans. Defenders of illegal immigrants say the opposite. Some claim that his is like a new Mexican invasion.