Hi
I don't know too much about evaluations in the USA but In the UK when you receive an evaluation it is something like this:
At an evaluation if something comes completely out of the blue to you it is an indication that there has been a major failing on the part of your line manager. In other words if they had concerns and did not manage them prior to the evaluation then they have a bit of a cheek bringing it out of the blue.
If it is something that you admit yourself requires improvement and both parties agree that something has to be done then your employer has to provide the resources and support in order to help facility this improvement. They cannot just demand improvements without reasonable justifications and support.
All employers must provide a safe and supportive work environment. They cannot say or promote the idea of "getting your act together or your out" without again providing support and clear indications of where imporovement is required. If this is not provided then it could be conceived as constructive dismissal and would be difficult to defend.
There should never be any major surprises at an evaluation. If there are, it is a sure sign of failings within an organisation and poor management at a senior level.
If they set a timetable for improvement it must be fair and reasonable. If you think it is not, then tell them.
Evaluations are a two way process. If you believe they are wrong then let them know and tell them where they are going wrong.