Since getting them to do that is literally the purpose of the nonsense currently being executed, and which has been executed against immigrant and nobimmigrant aliens for the last several years, I think you are mistaken. It's not like that's been at all a secret.
This image now is a lot nearer to reality than it previously was. When this leads to people not having US-citizen children, or not buying houses, or just not jumping on the boat to reach the US come what may, or just not being too optimistic in general (essentially not tying yourself to a country when the country hasn't done the same with you in terms of citizenship), things will maybe get a bit more sane.
> has to be based on the employer's decision to continue their employment and not some politician's whim
While everyone here would love for this to happen, clearly nothing's working as it should be, or how we want it to be. It hasn't been, for quite a while. This is realpolitik.
The only way this nonsense will change is when more people who do have other options take them. This is mainly an image issue; in the Obama years, even though it was probably as bad as this today (just not overt), the risk-reward ratio of surviving all this was viewed as better than going somewhere else. All this changed with Trump being this transparent. There is going to be a lot of hesitation now for anyone who wants to immigrate. Anywhere except the US, and only if necessary.