Is renting out territory for a foreign military base such a big deal?
Short answerThe base can draw its host into another power's conflict, although Greenland already belongs to NATO through Denmark and already has strategic exposure.
NotesA military base attracts the adversaries of the power using it. Its host can therefore become involved in a conflict it might otherwise have avoided. Greenland is already part of NATO through Denmark, so the hypothetical starts with existing alliance obligations and military exposure. Danish patrol vessels also supply specialist Arctic capacity that would be difficult for the United States to replace quickly.