Which, I mean, yes it is. Kingdom of Hawaii was a thing. The real difference is that Greenlanders are legally able to vote for independence whenever they feel like it, and have chosen not to, for economic reasons. So by that logic, Hawaii is more oppressed than Greenland.
That's where political pressure comes in. For example, Denmark is making many billions of dollars each year from the sale of GLP-1 drugs to the US. The US could just choose to negate those patents, stop those sales, and manufacture the drugs domestically with immediate effect. Other such levers like these probably also exist.
Ok, what pressure - other than violence - will be brought to bear on the poor Greenlanders.
Sounds more and more like voting in the Donbas.