

Any US company that wants to could setup mining operations in greenland today, Denmark/Greenland would happily welcome the development.
The reason the USA wants to seize greenland is because it foresees a future where it is no longer allied with Europe, so in order to secure the resources and military access in the long term they are annexing it now since Europe is entirely incapable of stopping them at present, both politically and militarily.


By Wikipedias count there are presently 51 on-going national emergencies in USA, 19 of them have been declared by Trump.
The oldest still active one was made by Carter in 1979, it’s a sanction on Iran.