Won't have to buy Greenland if his army invades it instead and declares war on a NATO partner, Denmark. Rump doesn't like NATO anyway.
One wonders why he wants it anyway. Greenland icecap is melting at a much faster rate than predicted. It was thought the runoff might be bad in 2070, and it is worse than that this month. If all the ice goes, Greenland will be just a ring of small islands, and ocean levels around the world will be 5 meters or 16 feet higher. Say goodby to all ocean ports, most beaches, a lot of national capitals:
Most of Wellington
Also major coast cities like
some of San Francisco
many others around the world.
Quite a few Indian and Pacific Ocean islands small countries