80%? Maybe, I guess? Before I give the short answer, here are my two longer recent public disquisitions on the subject. (There are others from over a decade ago out there somewhere and private ones for a certain senator from a sunny state.)

noelmaurer.com/p/the-pr…

noelmaurer.com/p/buying…

The short answer is that I can't judge proportions, but sovereignty gives three benefits we don't currently have:

(a) The right to subsoil royalties;

(b) The right to ban exports;

(c) Insurance against future Greenlandic perfidy.

The question is whether the American government values those benefits at a price than Greenlanders (not Danes!) are willing to accept.