My brother wants to adopt his daughter to me and immigrate to America with me.

You need someone to help you manage your account! In order to show that she is your daughter, you can also issue relevant birth certificates when applying for immigration. Ask your brother to handle this matter. Generally speaking, it is unlikely that you will go to America through adoption! You need to deal with all aspects of your niece's identity. The key is whether you want to be troubled or not. In fact, if you don't want to do this, just refuse him!