Well if the N-600 is that expensive to file, then I'll just apply for a passport for the time being.
You could still explore the possibility of requesting an N-600 fee waiver and check if you qualify for the fee waiver.
See the links about I-912 above.
But I agree, it will be something nice to have, and I will file for it. Probably next year.
I am very grateful for your help. I had never even heard of the CCA, and neither had my mother. I probably would have wasted tons of time and money renewing my GC and filing for citizenship next year without your help.
As a matter of fact, as pointed out by the posters above, it seems likely that you have derived U.S. citizenship through your mother even earlier, namely in 1996 when your mother naturalized.
First, it seems that you actually became an LPR in 1993, not in 2003.
In your posts above you mention that in 2003 you received your "new green card" and that you had been a "resident" for 20 years, since 1993.
You would have almost certainly become a GC holder in 1993, when your mother came to the U.S. and received a GC herself.
A regular green card is ordinarily valid for 10 years (although the underlying LPR status is permanent and does not expire). So you had to renew your card in 2003 and got the card that you have now, which is expiring soon. Note, however, that while a green card needs to be renewed every 10 years, the LPR status is continuous and does not expire (even if you don't renew a green card on time, you still remain an LPR and retain GC status).
On the front of your green card there should be a field "Resident since" with a specific date written there. Presumably for you it says "Resident since [specific date/month]/1993. Whatever the "Resident since" date is printed on your card is the date you became an LPR.
Now, even before the Child Citizenship Act of 2000 came into force, there were other provisions in the law regarding automatic derivation of citizenship by children of U.S. citizen parents. Prior to CCA these provisions were governed by the (former) Section 321 of the Immigration and Nationality Act. In general, these former INA 321 provisions were more restrictive than the CCA provisions, but in your case it looks like you qualified for derived citizenship under these former INA 321 provisions anyway.
See the USCIS Policy Manual,
http://www.uscis.gov/policymanual/HTML/PolicyManual-Volume12-PartH-Chapter4.html,
section "Acquisition of Citizenship Prior to Child Citizenship Act of 2000".
It says:
"In general, a child born outside of the United States to two foreign national parents, or one foreign national parent and one U.S. citizen parent who subsequently lost U.S. citizenship, acquires citizenship under former INA 321 if:
1) The child’s parent(s) meet
one of the following conditions:
a)Both parents naturalize;
b)One surviving parent naturalizes if the other parent is deceased;
c)One parent naturalizes who has legal custody of the child if there is a legal separation of the parents; or
d) The child’s mother naturalizes if the child was born out of wedlock and paternity has not been established by legitimation
2) The child is under 18 years of age when his or her parent(s) naturalize; and
3) The child is residing in the United States pursuant to a lawful admission for permanent residence at the time the parent(s) naturalized or thereafter begins to reside permanently in the United States."
Since your parents were divorced in 1990 and your mother received joint legal custody of you, you did satisfy 1c), and you also satisfied 2) and 3) [well, for 3) you have to make sure that your "resident since" date in indeed in 1993 and not in 2003].
In that case you would have automatically become a U.S. citizen in 1996, when your mother naturalized.
If so, you have a claim to derived U.S. citizenship both under the former provisions of INA 321 and under the subsequent provisions of the CCA.
In practice it does not matter very much which of these two claims is used (it will only affect the date to which they'll back-date you as having become a U.S. citizen). However, when you apply for a U.S. passport (and for N-600 if you chose to file it, now or later), you should probably mention both of these two bases for your claim to derived U.S. citizenship, and let the adjudicating authorities sort out the details.
You should try to get both your preschool/elementary school records from the 1996-99 period showing you living with your mother, and your school records for the period after Feb 27, 2001 showing the same.
Plus you'll need your current green card, your birth certificate, your mother's naturalization certificate, your parents' marriage and divorce certificates and the relevant custody papers (usually contained in the text of the final divorce decree) granting your mother joint custody of you.
Be careful with copies vs originals. For N-600 you only need to send copies, but for a passport application they generally want to see originals of certain things. For a passport application usually the original of the main document used for claiming citizenship needs to be enclosed, and this document gets returned by mail to the applicant when the passport is issued. E.g. for natural-born U.S. citizen such main document is the U.S. birth certificate, and for a naturalized U.S. citizen applying for his/her first passport such main document is the naturalization certificate.
In your case they'll probably take your mother's original naturalization certificate (which will get mailed backed when your passport is issued). However, it may well be that for your passport application they'll want to see the originals or at least official certified copies of some other documents mentioned above (marriage/divorce certificates, your birth certificate etc).
