adult adoption within US & change of visa status

People can be adopted only under the laws of their country of citizenship. For instance, a USA person can only adopt a Chinese adult if Chinese law allows it. (Which it does not.) And adopting a person over the age of 16 will not have any impact to the person's visa status. US law allows for an adoption visa to be granted to children under 16, but not to those over 16. And there is no other type of visa that allows their status to be changed solely on the basis of having been adopted.