The federal Americans with Disabilites Act (ADA) protects disabled employees (including autistic employees) to retain their jobs with reasonable accommodations. If employees can't perform their jobs even with such accommodations, their employment may then be terminated.
However, employers may be found in violation of the ADA for failing to accommodate. This appears to be the matter at hand.
Gather as much evidence about your claim as you can while you are still employed. Record the dates and supervisors to whom you have complained, and their replies. Keep everything in writing. Ask that they reply to you in writing, as well. If you have witnesses among your coworkers, ask them to write statements about what they have witnessed (they might not want to get involved, so you can write down what they have told you).
If your employment is terminated or you have been given a written warning of termination, find a workplace-discrimination lawyer. Every state and most major cities have nonprofit groups with these lawyers. If you can't find one, try your local ACLU.