I am urging you to go into the rest of this comment with an open mind.
H-1B visas require a “prevailing wage” which the foreign worker must be paid at or above in order to get a visa. Prevailing wages are made based on the area the worker will be in and their title, and are published on the DOL website: https://www.dol.gov/agencies/eta/foreign-labor/wages
Before being allowed to hire a foreign worker a company must advertise the position in the US. This could be improved as right now you can put the ad in the most obscure newspaper you can find or on TV at 3am. But you do have to do something.
The decision to grant or deny a visa is made by a consular officer - a trained human - who carefully considers all the foreign worker’s case materials (called a “petition”).
All this is to say, they thought of this “bringing in foreign workers depresses wages” problem way back when they created this program and invented prevailing wages to mitigate it. They thought of “bringing in foreign workers denies locals opportunities to apply for those roles” way back when they created the program and invented job ad requirements to mitigate it.
Don’t get me wrong the H-1B is definitely being exploited. Bodyshops are a thing. But it’s not at huge scale. It is a problem to be fixed with better enforcement and targeted reforms, not pitchforks.
Mr. Sanders’ argument needs to be backed up differently. As it stands he is misleading the public. It’s surprisingly out of character.