Land has been purchased and sold between nations throughout human history. The Fed has nothing to do with the feasibility or possibility of purchasing Greenland.      Name one time a country sold itself to another country and it didn't become part of the purchasing country?   Thinking of Alaska or Louisiana purchase?  Thinking of Mexico/Texas?   Did we buy Puerto Rico or Guam?     The only time you buy land is to incorporate it into your country.   Otherwise you get a situation like Hong Kong where when the deal's over you have an occupation and forced assimilation.