Arthurs Quest 1999 on netflix

To escape the clutches of the evil warrior and sorceress Morgana, Merlin transports young King Arthur into modern day America. When Merlin comes back ten years later to retrieve him, he finds a hip 15 year-old Arthur who does not believe Merlin, nor does he want to return to the past. Merlin must convince Arthur of his true identity, before Morgana can retrieve Excalibur and allow the Dark Forces to take over the world.