In the US, there's no federal law on constructive dismissal so there are variations, however, generally, constructive dismissal is not always the same as unfair dismissal, although we most often hear the term come up in conversations about an unfair constructive dismissal.

There are also a significant number of ways you can 'manage someone out' which are not any more 'constructive dismissal' than 'quiet quitting' is 'constructive resignation'.

For example, reducing flexibility in things like lateness policies, shift swaps, holidays, etc. is likely to be unpopular, but as long as it's applied fairly across all employees, would not likely be found as unfair, but may well result in people quitting.

Ok fair, if you're being nasty to everyone it's not discrimination at least

They get sued, the cases will usually be settled out of court.