Employment in the US is "at will", which means you can be fired without just cause (except for prohibitions for race, religion, gender, age, disability, national origin). It may seem terrible, but it's good to remember that "at will" works the other way too, so if your situation sucks you shouldn't feel legally obliged to stay.

[edit] Also, I'm sorry that you got fired like this, it sounds maddening and inhumane. Best of luck to you in finding something better.