They exist but primarily protect private people. If the court determines that you are a “public figure” (I forget the legal term; IANAL) — such as CEOs of publicly traded companies, or politicians, etc. — then the bar for winning a case for defamation goes up significantly.

Furthermore speech that is essentially opinion or critique is a defense against defamation that can cause the case to be dismissed before trial. 1st Amendment protections from the US Constitution.

If you’re careful to word what you’re saying as a statement of your opinion rather than an assertion of fact, then a defendant has little chance at winning a defamation lawsuit from what I understand.

Lastly, if what you’re saying is factually true then that offers an absolute defense against a defamation lawsuit; you would need to be able to prove that however.

There are some country-wide precedents that SCOTUS has ruled on; otherwise laws are set by individual states from what I understand.

https://en.m.wikipedia.org/wiki/United_States_defamation_law