I am confused by your post.
Did Megan and Harry take the baby with them and the baby is now in the U.S.?
Or...Did the royal family take Archie and the baby is now in the U.K. under the care of the queen?
Baby is in US being well cared for by nanny who loves him as his mother does not. Every nanny quit because Megan was impossible to work for until this one.
When and if they travel to England they leave him in US.
The queen has legal custody of all her progeny, and if they ever take Archie back, Queen can take him, declaring his parents unfit. Therefore, they NEVER take him to England with them because they know they are not good parents. Queen will never see Archie again. Very sad, she was clearly happy with him when he was first born, far happier than MeAgain.