Putin made it very clear....Russia have NEVER extradited someone seeking asylum....and neither has the United States.
Sorry but you are wrong. The US returned a Russian seaman Simas Kudirka in the 1970’s after he physically jumped his ship and swam to an American one.
When he was returned, he was sent to a labor camp for nearly 10 years before we got him out (I think it was Reagan who did it).
There might have been some Cubans who were also returned (Elian Gonzalez, as an in loco parentis case).
By the way, Snowden should be shot as a traitor.