You haven't stated any facts which would support suing the county as to a lien for child support. If you owe the money, you are required to pay child support unless you can compromise the arrears. Or, if there's a bona fide mistake, you can correct it. The County is there to provide a public service. Do you owe the money? Can you work something out with them. If there is a modification of support in order then you would have to request it. It's not automatic. Just a suggestion: threatening to sue an agency is probably not conducive to a resolution of the issue. If you have a question about what transpired, check the court file for the paperwork. You may also have a statute of limitations issue.
Ms. Johns is a lawyer although she is not your lawyer unless you have consulted with her and signed a fee agreement or letter agreement confirming her representation of you. This post does not constitute legal advice and no attorney client relationship results.
With all due respect, I think it would help if you started off at the start and tried to work through the issues relating to the lien that was filed instead of trying to jump to the end and start suing everyone for everything you can think of. For example, if the lien really was filed in the wrong county, and if filing in the correct county is necessary under CA law before the lien can be effective, then you might have grounds to have the filed lien cancelled and get a second chance to address the issues in court. You might also have other grounds for review available to you that should be pursued before you get to the point of suing everyone for everything; it's really only after you've exhausted all reasonable administrative options that it makes any sense to start suing the agency in question.
To that end, instead of fishing for lawyers here, it would be more useful if you consulted with a local attorney with expertise in child support proceedings, if nothing else to get a more concrete idea of what your options are. Depending on your financial resources, I would suggest that you contact your local bar association or lawyer referral service to get a referral to an attorney who will discuss your case with you for a small or nominal fee. I would also suggest that you contact your local legal aid society to see if they can provide you with some assistance.