You could try FOIA for your mother's A file - if she naturalized, it would be in there. Then you'd also want to get records from your mother's time in the US - school, doctor, work, and similar (baptism/christening if applicable). Then you want to see what rules were in place for getting citizenship through a parent at that time - sounds like your father was a USC? Same records search as for your mother but with a twist that you'd need him to recognize you since he's not on your birth certificate if you want to proceed to being recognized as a USC. This all will involve a lot of legwork, time, and possibly money with potentially needing some or all cooperation from your family members.
Where were you born? I'd imagine DV lottery if you qualify would be one path to get to the US if you can't find solutions through family.