If Outer Manchuria had a large Chinese and Korean population before the Russian expansion would it be a part of Russia what would be the consequences of this...
It depends
Maybe Russia wouldn't get it in the 1850s, but that leaves a lot of time when they could, and the era of appropriation of Chinese territory doesn't have to stop then - it could be as a result of intervention later, or a wholly Russo-Chinese War later
If the Russians don't hold the Far East, they probably won't control Northeast Siberia-or Alaska. This puts Alaska in Canada. Northeast Siberia might be Chinese, Japanese, Manchurian, or even Korean.
They already HAD NE Siberia and Alaska, that's why the Crimean War was fought around Sakhalin and an assault on Petropavlosk, which was the main naval base before the acquisition of the Maritime Provinces and the founding of Vladivostock
If Manchuria has a dense population earlier in 13-15th centuries, I believe that america would be discovered earlier by easterners.I'm pretty sure that the OP relates to the 16th century and before as a PoD, and you're hung up on 19th century OTL stuff.
I expect that the Russians will be able to take northeast Siberia regardless, all the way out to Kamchatka, but logistics will be much more difficult.
If Manchuria has a dense population earlier in 13-15th centuries, I believe that america would be discovered earlier by easterners.
Hmm, kinda like a crime.
Opportunity: No Ming-like enforced ban on ocean travel.
Method: Craft capable of reliably making the trip (nasty weather there).
Motive: Tricky. Trade is unlikely-who's there to trade with?
Say a maritime culture develops in the region (which would presumably colonize Sahalin, Hokkaido and the Kuriles); could we see long-range fishing expeditions, like with the Basque? If they go far enough, they'll find the Pacific Northwest, and eventually word will filter back to merchants. Problem is, the locals there are hunter-gatherers, albeit unusually rich ones. Kwakiutls or whatever might be happy to trade, but it'd be low-volume stuff. Not big enough to justify, say, major exploratory expeditions.