The law doesn’t say who you can or can’t name to take care of your children. Besides having to be over 18, there are no other specifics and there is no US citizen requirement.
You want to choose someone that you trust to make decisions about your child, either a family member, close friend, or neighbor, or another responsible adult. Make sure the person is willing to care for your children. Also, let your child know who to go to in an emergency.
The person does not have to be a citizen, but remember, they won’t be able to transfer care of your children to someone else if something happens to them. DOPAs are not transferrable. So, if you are worried about that, think about listing an additional person as an Attorney-in-Fact.
If the person you want to care for your child lives in another state, you need to find a form for that state. Minnesota DOPAs only work in Minnesota. Many states have similar laws and forms that let you do the same thing. It doesn’t mean you can’t travel with the child, but it could be an issue if the child is moved to another state. If you have questions about doing a DOPA in another state, talk to a lawyer who is licensed in that state.