[badRNG]

There's no grounds for a lawsuit, not in the states. They can legally fire you for nearly any reason or for no reason whatsoever. All PIPs do is help the company fend off claims that the employee was fired for an illegal reason (e.g., for being a member of a protected class, retaliation, etc.)

[lowbloodsugar]

PIPs would do that if the process was valid, but as pointed out, they are not. So if they defend against a claim of racism, sexism, castism, or ableism, with “but PIP!”, then it helps if we can show that PIPs are bullshit.