I'm just curious, because geographically far eastern siberia is so close to the far west of north america, knowledge of the continent could have found it's way to europe that way?
all of the accounts I know of involve explorers reaching the American continent from the East - did anyone come from even further west?
Well, the Russians discovered Alaska from Siberia. It is possible, though not definite that Dezhnev reached Alaska from Siberia in 1648. It is certain that Bering and Chirikov discovered Alaska in 1741.
Of course, it is assumed that the distant ancestors of Native Americans reached North America from Asia back in the depths of time (probably several times).
There is no evidence that other Asian civilizations explored to North America.
Being able to discover new land doesn't just involve geographical proximity, it also involves having ocean currents that would enable a boat to sail to the new land. There are cases of ancient civilisations, in particular the Polynesians, who managed to discover new lands by sailing against the prevailing winds/currents, but in general a boat would have preferred to sail in the direction of the prevailing currents/winds.
Taking that into account, here one can see a crude map of the world's main ocean currents. So even assuming there were civilisations in the Far East of Siberia that could build ships capable of voyaging across vast expanses of ocean, the currents would simply bring them south towards Japan. From the currents alone, the most likely people to have reached North America would have come from Japan. I haven't heard of any evidence of Japanese voyages to the Americas, but I could be wrong.
