He should knows that the United States has a trade surplus with Spain; it benefits more from that relationship than Spain do.
We buy a lot of space vehicle components from Spain used for national defense (Airbus primarily). Not sure what the justifitication is here.
Spain has a lot of friends in the EU and given the way Trump has bullied and insulted all of them lately this is probably going to backfire and lead to them becoming closer together to resist trump more. I feel like this is basic psychology. Nothing makes groups gel together like a common threat.
All according to plan if you believe that Trump is a foreign-sponsored "useful idiot".