I don't think the regulators are needed. These are apparently unionized workers who can and have been sticking up for themselves.
Even non-unionized workers in the US will be able to negotiate fair working conditions with TSMC because they have options. Many other local businesses would probably be happy to employ these same skilled workers.
The problem here is that that's exactly what's going on and then TSMC says "We don't get enough skilled low-cost labor, so we'll just have to bring in our own from Taiwan. It's all YOUR fault we do this! We so want to use Americans, but, you know, there just isn't enough!".
I can totally see why they do it, but it's bad and dishonest. What they've now given themselves are two things:
If regulators do come and ask "So, what's up with all the non-Americans working on this?", they can answer "Cause there isn't enough!", and if the extra capacity is needed (which doesn't seem to be the case), they can just say "Well, if the Americans would have been good and fast enough, we wouldn't be in this situation! Sorry! Not our fault!".
Complete BS, and I was just waiting for this after the last rant about that was something along the lines of Americans workers need the passion to work long hours for low pay.