This is how it's supposed to work in America, there are certain reasons why I can't fire you; like race. But I can fire you for anything else. But in reality this only holds true at smaller firms. At larger firms, they still need to document, because if I fire you for some random reason (which is legal) you can sue me saying that I really fired you for an illegal reason

This really only happens at larger firms, 'cause you could sue me, but you wouldn't get enough money out of the deal to properly pay your lawyer.