The government can not keep illegal drugs , alcohol or cell phones out of maximum security prison cells , how do you expect them to stop people from coming into this country ?
A lot of people came in thru Ellis island, but the government did not have a Ellis island type place on the southern border.
Some say the definition of a country is a shared common history and language.
Do South Americans that live here want to become citizens of the United States of America or do they want to keep Spanish and celebrate South American history and customs ? But love the fiscal advantages ?