As you can see by the pic in my sig, my DD is also African American. I adopted through a private agency which works on domestic as well as international adoption. I was amazed by how many caring people seemed to not even really consider adopting domestically. Some were adopting children from Africa so it definitely was not about race.
As the article notes, there are many reasons but here are a couple I've noticed:
1) It seems like there is more acceptance in general of international adoption that crosses racial boundaries. Unfortunately, that's not always the case for domestic adoptions. There are some states that won't let a caucasian family adopt AA children.
2) I think there's a general belief that children in need of adoption in the US are still so much better off than children in other countries. I don't doubt that is true but I still was so much more interested in adopting domestically after just a little soul searching.
As I said, I adopted through a private agency and did so because a single parent adopting through the state has very limited options. I respect people who adopt special needs children but I knew that such a choice was not one I could make, especially since I am single. Also, I hoped to adopt an infant and knew that I would be very unlikely to get such an opportunity through a state adoption.
This was the best decision I ever made. I've had people make comments about how wonderful I was to adopt her. I respond by saying that I am fortunate I was able to be her mother and that I am so grateful to her birth parents for making such a hard decision. BTW - They participated in selecting me as the one to adopt their birth daughter.
One thing I wish would happen is that the states would do more outreach in the AA communities to let people know about the need for adoptive parents. A former co-worker once asked me about my adoption because she was considering that route for herself but didn't think she could afford it. I told her as much as I could about both private and state adoptions and I think she was surprised to hear that state adoptions were so inexpensive. A friend adopted 2 children through the state and I'm pretty sure she and her husband had all the adoption expenses reimbursed once the adoption was final.
One last thing and I'll get off the pro-adoption soapbox

If anyone reading this is considering adoption (or knows someone who is) but is pu off by the expense, please check into the Federal adoption tax credit. I think you can now get a tax credit of up to $10,000 of your adoption related expenses!