On the above I would correct that it’s not “US Citizen” but someone with full employment eligibility, which could be for example a Green Card holder.
That doesn't matter if they all find a new job very quickly, what's more relevant is the unemployment rate. Is it increasing?
At least when it comes to the overall unemployment rate, it seems to be very low when I see articles like this: https://www.businessinsider.com/december-jobs-report-labor-m...
I didn't find IT-specific stats to be fully sure (well it's somewhere on https://www.bls.gov if you're so inclined), but I'd be surprised if the IT industry were much worse (if at all) than the average over all industries.
The truth is that they can't find someone with the skills who will work like a pittance and who will worry about being deported if they leave/get fired.