ONECELAND: Answer

If you convert ONE in ONECELAND to the Roman numeral I, the result is ICELAND.

Doing likewise for SNONENENLAND:
1. Change ONE to I = SNINENLAND
2. Change NINE to IX = SIXNLAND
3. Change SIX to VI = VINLAND

Vinland was the name that Lief Erikson gave the coastal area of North America he and his men began visiting around the year 1000. Born (most likely) in Iceland, Erikson launched the expedition from his home in Greenland.