Not sure why right-wingers keep crying about it.
Illegal immigration was increased due to free trade. What happened as soon as free trade started sister cities on the Mexican side of the border near America, began to grow and attract people from central America, and southern Mexico.
It started with Tijauna. When American televisions started being assembled there, Tijauna became more than just a group of brothels.
It became a large industrial center like several other Mexican cities along America's border.
As jobs grew, so did population as people were drawn from central America and southern Mexico. But when jobs were filled and people arrived in these cities and could not find jobs, they continued north into America to find a source of income.
The reason why these cities became industrially strong, is it was cheap to do the labor there and cheaper to be that close to America, so transportation for the finished product wouldn't be as costly.
Right-wingers got what they wanted, and like usual want to cry about the effect.