Is there any validity to this speech from Bernie Sanders and H1-B visas. Are Americans losing jobs to immigrants to make corporations more profitable?

Is there any validity to this speech from Bernie Sanders and H1-B visas. Are Americans losing jobs?

"As many as 33% of new IT jobs in America are being filled by guest workers. According to the census, there are MILLIONS of Americans with advanced degrees in science, technology and math that are not currently employed in those professions. We tell kids, go out, get involved in STEM work, become a scientist, an engineer, and then we bring in people from abroad to fill the jobs that they were educated to do. Adding insult to injury, half of the top 30 H1B employers are companies whose major function is to outsource American jobs, known as body shops."

"If there is truly a major shortage of skilled workers in this country, why did Tesla lay off over 7500 of tech workers in 2024, while at the same time applying to hire thousands of H1B guest workers? If these jobs are only going to the best and brightest, why has Tesla employed H1B guest workers as associate accountants, for as little as 58,000 per year? Associate mechanical engineers for as little as 70,000 per year? Those occupations don't sound like highly specialized jobs as Mr. Musk claimed last month."

"Why are H1B guest workers being employed as fashion models, lawyers, dog trainers, cooks and english teachers?"

"It is simply not true that the H1B program focuses on the very rare and highly skilled workers that American companies cannot find."

Source: https://www.youtube.com/watch?v=Sxn-tyuKBus&feature=youtu.be