As it is, the welfare state necessitates harsh immigration policy. There's a strong correlation in the U.S. with the decrease in the employment of blacks and young people and the increase in immigration (illegal and otherwise). Basically the U.S. government policies cause huge incentives for immigration from Mexico:

1. Drug war is destroying Latin America, resulting in millions of would be emigrants who must seek a better life, often at great personal risk.

2. Farm subsidies, especially corn, allow the U.S. to export products so cheaply that it can be sold in Mexico for less than the local farmers can produce it. Basically we're destroying Mexico's primary sector, so where before those people were merely fucked because of gang violence, now they're fucked and unemployed. Not to mention the subsidies create more farming jobs in the U.S. than there would be in a free market, and immigrants from Mexico of course seek those jobs. They reduce the demand for labor, and thus, the price. Low-skill indigenous workers in the U.S. suffer lower wages and higher unemployment.

3. Welfare benefits create added incentive for this flow of low-skill workers into the country, and for the currently low-skill workers to remain having low skills, exacerbating every one of the above problems.