> where the hiring company has even looked for US applicants
I've worked at a company where >90% of the technical interviews I conducted were H1-B hires. It makes perfect sense for a tech company to bias the applicant deck in this way for a few reasons. They're willing to accept a lower comp package. Once they're onboard, they will generally keep their head down, do whatever they're asked to do, and accept whatever working conditions they get without complaining. That said, I've known several brilliant H1-B workers. However I've noticed that they rarely stick their neck out and challenge the status quo, which can lead to bad ideas receiving unquestioning and persistent efforts to implement in spite of the writing being on the wall about that project's inevitable demise.
I've worked at companies that hire primarily non-H1-B workers, and I can tell you that the amount of complaining about working conditions in particular at those companies was a couple of orders of magnitude more raucous. The end result of a complacent workforce was a soulless office with ubiquitous infrared sensors, no available meeting spaces, a microkitchen stocked with a pittance of moldy food, and with floating workstations where the equipment was chronically broken or missing.