If one takes a polar view of Greenland, it is obvious that it sits directly between the US and Russia's ICBMs. As such, it is in an essential location for early warning systems and ICBM defense. Unless it becomes part of the US, there is no way to enforce territorial sovereignty over the waters surrounding it. Without this, US adversaries can place naval and air forces much closer to Greenland, allowing them to perform a quicker strike against US defenses.
Why is this so hard to understand?
Why is this so hard to understand?