An American version of Doctor Who was already tried, way back in the early 80's. it was called "Voyagers" and it was about a time traveller from a different planet who bounced around earth's past to learn more about us, had a 10 year old boy as a sidekick (which became real creepy, at least the Doctor had a thing for grown up companions). Instead of a Tardis, the traveller used something that looked like a pocket watch. And who could forget Time Tunnel? please, leave time travelling to the professionals!