You used to be able to get hired and taught on the job, now the employers expect you to pay your own way through a technical school for several years before applying for a minimum-wage job. So you've got (a) lower wages (b) you need to pay to educate yourself (c) you need to pay to support yourself during those years of training and (d) you're guessing which job skills are going to be in demand after N years, so after spending the time training and taking on debt there might not even be a job waiting for you.

I feel like the whole question here is simply: how much commitment to the existing US labor pool should US laws/regulations require from US employers?

Over the last decade, the answer has been "not much." But, now, because of political and economic realities, that answer might change.