At what age, a child born in the United States can enter the country, in the company of another person who does not have custody.
If there is someone waiting for you or claiming, you can enter alone, if you are born in the USA. Age should not matter if you’re a citizen. But in the company of an adult.
If you are born in the US then there is no age, if you can verify that you were born here. BUT. There may be a legal battle for your custody. A judge and jury will almost always return you to your legal guardian, no matter in which country you live. There may also be charges against the adult who removed you from your country. It would be considered kidnapping of a minor, or even human trafficking.