The reason why Trump thinks that it might be effective is that the economic consequences might be negative and that will politically harm politicians. But if Trump is hated, telling him to fuck off is politically beneficial.
I suppose there are also security concerns. Could he put a lot of pressure on NATO and Spain's membership which would certainly cause a lot of pain. I know Spain is far from Russia and all but he could refuse to sell them any parts and weapon systems.
Just saying, why poke a pile of shit and then get it all over you. Trump is temporary and best to just quietly wait it out, unless you want to smell like shit.
I'm sure losing their jobs bothers anyone, but my might is they won't assign it to Trump.
If Trump behaves badly threatens Europe and then countries don't let him use bases, who's at fault? Trump.
In fact people might lose their jobs and assign it to the chaos created by Trump. He doesn't care, of course, my point is if people don't assign it to their own politicians, then the trade thread isn't effective.