OMG! You are ME, two months ago and I know exactly how you feel.
Instead of telling me during our weekly brainstorming sessions, my supervisor waited until my three month review to open the floodgates.
I took responsibility for the errors but deep down I saw the writing on the wall.
Like you, I'd rather have been told all along if my errors were that blaring and knew they were building a case against me.
That was two months ago and the hoops i had to jump through made the circus look like child's play.
I still feel icky having been let go and all but am very relieved. The job consumed me to the point of having major depression and inability to enjoy anything.
I don't know your situation: Is this a fairly new job? Do you like your job?
My job was new and I wasn't crazy about it. I also knew that I did not have a flying chance with my incommunicative supervisor.
Can you respond to your meeting in writing and CC HR? It didn't make a difference in my case but it made me feel proactive.
Good luck.
If it doesn't work out then you deserve better.