It's not a stunt, it's total megalomania and you are falling for the coping tactic of pretending he's not serious in his literal statement to expand the borders of the US north and south.
If you focus on every single one as gospel you'll be tripped up both ways. He is a walking contradiction of statements
In his first term he told North Korea there'd be "fire and fury like the world has never seen" and then the next minute was cosying up to him in a summit
He says anything and everything. He is certainly expansionist don't get me wrong, but focusing on individual statements will lose you the picture of where he is serious and where he isn't
Focus on who he appointments, what actions they take, what executive orders he signs, what he does with the military, etc.