My friend filed a petition for an adult child (over 21 years old) six years ago and just received notification this year that there's a visa number available for the child. Meanwhile, the child has traveled to study and obtained a permanent residence in Canada. However, the child still wants to join his mother to the United States. Will the US give the child a GC if all the requirements are met?
Sure. The fact that he is in Canada is not an impediment.