The US has played by different rules, might makes right, in the western hemisphere for a long time.

Screwing around with Greenland shit, on the other hand, seems riskier.

In practice the US could already do whatever it wanted in Greenland/Canada etc. The options for the motivation behind the theatrics I see. 1. Instill fear in the vassals->support for militarization rises there->they become more useable as proxies against RF/China 2. Just another Trump silliness