With it being so much relatively closer than to Europe, how come Asian counties or Russia hadn’t sailed east prior to Christopher Colombus’s discovery?
I'm not sure what you mean by relatively closer. The pacific is much larger than the Atlantic, so it would have made the chance of an Asian nation stumbling across the Americas smaller. In addition, by the time the Americas had been discovered, Russia didn't even exist. Tsarist Russia only began to exist with Ivan the Terrible in 1547, and the Russians wouldn't get to the Pacific until the 1600's.