Immigrants got most of the benefit from economic growth in last 14 years

Center for Immigration Studies:

Government data show that since 2000 all of the net gain in the number of working-age (16 to 65) people holding a job has gone to immigrants (legal and illegal). This is remarkable given that native-born Americans accounted for two-thirds of the growth in the total working-age population. Though there has been some recovery from the Great Recession, there were still fewer working-age natives holding a job in the first quarter of 2014 than in 2000, while the number of immigrants with a job was 5.7 million above the 2000 level.

All of the net increase in employment went to immigrants in the last 14 years partly because, even before the Great Recession, immigrants were gaining a disproportionate share of jobs relative to their share of population growth. In addition, natives' losses were somewhat greater during the recession and immigrants have recovered more quickly from it. With 58 million working-age natives not working, the Schumer-Rubio bill (S.744) and similar House measures that would substantially increase the number of foreign workers allowed in the country seem out of touch with the realities of the U.S. labor market.
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There is much more.

What should be clear is that there is no real labor shortage in the US and the labor participation rate is shrinking to the lowest level in decades.  The case for permitting uncontrolled immigration appears to be weak at best.  This is another reason why there is growing opposition to the Democrats attempt to import voters.

The NY Times describes other reasons the immigration reform proposals are failing:

Bleak Prognosis From Both Sides of Aisle in House for Immigration Overhaul

For Republican lawmakers, distrust of the president and opposition from the Tea Party make action on immigration a daunting prospect.

He want enforce the current law, so why should he be trusted to enforce border security provisions of the proposed law?