Does the guardian I choose have to live in the United States?

No. Parents can designate any responsible adult to raise their children if they pass away, even if they do not live in the United States.  Ultimately, a judge must approve any parent’s nomination of guardian.  For parents nominating guardians who live out of the area, or even out of the country, it’s important to also designate local temporary guardians who can care for the children in the interim until the permanent guardians can arrive and assume their role.