One would have to happen before the other. You would need a much larger Norse influx into Gardariki in the 9th century, several times the number that came in OTL. They would also have to fail taking Kiev, because there were more Slavs in the south which is why they assimilated. But if you keep the Norse around Holmgard for a few more centuries, they would probably accumulate the population base to expand without assimilating.
ITTL there would probably be no Russians.
I am not as knowledgeable about Vinland, so I can't really speculate there.