If even just one person finds this blog post helpful, it will be worth it. I continue to be amazed at how hard it is for the thousands of parents who adopt children internationally to get this necessary information. I'm no expert but I've been through the process successfully myself.
If you have adopted a child from a foreign country and your child came home with an IR-4 visa in his/her passport (not an IR-4), you will need to "readopt" your child in the United States in order to get your child's Certificate of Citizenship.
Each state handles the readoption process differently and in our state (Maryland) each county handles it differently. For our readoption process, we basically had to run through the domestic adoption process.
To determine what you need to do to readopt your child(ren), go to the Child Welfare Information Gateway website - http://www.childwelfare.gov/
Click on the link for the National Foster Care and Adoption Directory - http://www.childwelfare.gov/nfcad/
You can go directly to the Directory but you might find other helpful information at the main site so I posted that link, too.
Select your state and the information you want to know - for readoption info, check the box for "State Foster Care and Adoption Officials." On the resulting page, find the contact info for the State Adoption Program Manager or similarly titled person. Contact that person and they or someone from their office should give you the details you need to know for readopting your child in your state.