If your child was adopted internationally, it is critical that he/she has proof of U.S. citizenship, such as a Certificate of Citizenship (COC) or a valid U.S. Passport.
One client recently recounted an encounter with the DMV when her child went to apply for her learner's license only to be turned away because the child could not "prove" she was a U.S. Citizen. It was upsetting to the parent and the child. The child IS a U.S. citizen but she was caught in the 2001 through 2004 gap when COCs were not automatically sent after completion of an overseas adoption. Read more from "Show Me Your Papers!"
The Child Citizenship Act of 2000 went into effect on February 27, 2001, granting automatic citizenship for most children who entered the U.S. on an IR3 Visa after adoption in a court outside the U.S. (Children entering on an IR4 Visa typically have to finalize their adoption in a US Court and then apply for COC.)
Even though an adopted child entering on an IR3 Visa may have become an automatic citizen, USCIS did not start automatically sending COCs until January 2004. So, in order to prove your child's citizenship, you need to file for a COC for your child if he/she came to the U.S. before January 2004.
A Certificate of Citizenship and/or a valid U.S. Passport are both evidence of citizenship, and in these times, I strongly recommend that you check your paperwork and consult with an adoption attorney to make sure that your child has one or both of these.