Americans are not being hired because the managers making the selection are only hiring people from their own region.
Talk to any American software developer who has spent the time trying to understand why, when their skills are current, they can no longer buy an interview.
Cutback in H-1B Visas Did Not Raise Employment for Natives, by Steve Maas, NBER Digest: In response to concerns that foreign workers were taking jobs from Americans, especially in high-technology fields, Congress cut the annual quota on new H-1B visas from 195,000 to 65,000, beginning with fiscal year 2004. A study by Anna Maria Mayda,Francesc Ortega, Giovanni Peri, Kevin Shih, and Chad Sparber, based on data for the fiscal years 2002-09, finds that the reduced cap did not increase the hiring of U.S. workers.
In The Effect of the H-1B Quota on Employment and Selection of Foreign-Born Labor (NBER Working Paper No. 23902), the researchers examine data obtained through a Freedom of Information Act request to present the first assessment of the consequences of the cap reduction on various sectors of the skilled labor force.
The H-1B program, which was launched in 1990, has provided foreign-born, college-educated professionals their main entry point into the U.S. market. As much as half the growth in America’s college-educated science, technology, engineering and mathematics workforce in subsequent decades can be attributed to H-1B workers.
Since the cap was tightened in 2004, firms hired between 20 and 50 percent fewer new H-1B workers than they might have hired had it remained at 195,000 visas per year. The researchers find, however, that the reduced pool of foreign workers did not lead firms to hire more Americans, and conclude that this suggests “low substitutability between native-born and H-1B workers in the same skill groups.” The cap only applies to for-profit companies, not to new employees of educational institutions or nonprofit research institutions.