Most all companies have at least a 90 day probationary period.
I live in a right to work state, basically you can be fired for a reason or no reason at all. Unless you belong to a union.
As far as suing them? The reality is the ADA is really more bark than bite unfortunately.
I seriously doubt a reputable Lawyer would even take the case. Sure you could find a shady lawyer to do it. But is it really worth it for a job you had for only 2.5 months ? You would be paying for a lawyer that likely won’t win so your out money too.
They have already shown you how they react to someone that needed time off for mental illness ... do you really think they are going to become more understanding ??
I’m sorry this happened to you. I hope that your able to get back on your feet and feeling much better. Good luck