If you believe this, it's not safe to fire
anyone --- all of them could "file costly wrongful termination suits".
In fact, "wrongful termination" doesn't mean "terminated unfairly". It means "terminated unlawfully".
In the US, unlawful termination occurs:
* When it contravenes an explicit clause in your employment contract or an implied contract you accidentally created.
* When it has the effect of discriminating against a protected class.
* When it violates the ADA.
Employers in the US generally have no obligation whatsoever to provide "reasonable time to take corrective measures". Things like PIPs have two purposes:
* As an attempt to bulletproof firings that target ostensible members of a protected class
* As a humane / bloodless way of notifying employees that they're about to be fired and should start looking for a new job.