This isn't true.
The whole premise of H-1B visas was that no qualified Americans could be found for the job, and that companies had to demonstrate that they searched for qualified Americans before pursuing the H-1B visa route.
Now, they may be gaming the system by making the "qualifications" unattainable, but it still is a requirement.
From USA Department of Labor: H-1B Program:
OverviewThe H-1B program applies to employers seeking to hire nonimmigrant aliens as workers in specialty occupations or as fashion models of distinguished merit and ability. A specialty occupation is one that requires the application of a body of highly specialized knowledge and the attainment of at least a bachelors degree or its equivalent. The intent of the H-1B provisions is to help employers who cannot otherwise obtain needed business skills and abilities from the U.S. workforce by authorizing the temporary employment of qualified individuals who are not otherwise authorized to work in the United States.
The law establishes certain standards in order to protect similarly employed U.S. workers from being adversely affected by the employment of the nonimmigrant workers, as well as to protect the H-1B nonimmigrant workers. Employers must attest to the Department of Labor that they will pay wages to the H-1B nonimmigrant workers that are at least equal to the actual wage paid by the employer to other workers with similar experience and qualifications for the job in question, or the prevailing wage for the occupation in the area of intended employment whichever is greater.
Key News
DOL Announces Plans to Protect American Workers from H-1B Program Discrimination: On June 6, 2017, the Department of Labor announced actions to increase protections of American workers while more aggressively confronting entities committing visa program fraud and abuse. Read More
-PJ
H-1B Is Designed to Allow Employers to Replace Americans with Cheap Foreign Workers
Replacing Americans with H-1B workers has been going on at least since 1994.
In 1998, Congress responded explicitly by making it legal for employers to replace Americans with H-1B workers. Under the current law an employer may replace an American with an H-1B worker unless:
You have to navigate through two levels of misdirection in the code to piece all this together. Congress went to a lot of effort to ensure employers can replace Americans and to hide that fact from the casual reader of the code.