That being said, now that he's backed off, it's probably better to focus on what comes next rather than continuing to debate on what he should or should 't have done.
Actually...
What Trump has very successfully done is leverage the axiomatic observation that npredictable strongmen spook predictable bureaucrats/bankers/career politicians.
Trump could’ve got to ABC simply by talking to Denmark as a pal - but nothing would’ve changed in EU NATO.
Even if the last week of bombast results in Trump walking back to the same ABC and Europe cooling its one or two jets, the message it sends out to EU-NATO (especially after Venezuela) is, “seriously - don’t screw with THIS President.”
I suspect what comes next is what could’ve happened anyway - Trump invokes the clause from the ‘51 agreement to renegotiate/extend the scope of US in Denmark, and gets what he would’ve got anyway, but the rest of EU-NATO decides to reduce their dependency on the USA - the US reduces its bases across Europe, and redirects resources from France and Germany to Greenland.
But instead of Trump coming out of the process looking like a stable statesman, he comes out looking like a hair-triggered strongman.
Agreed.