Trump can put an instant stop to this talk.
Trump “Try this and there will be zero trade between the EU and the US...and NATO will have to survive without a cent from the US and ALL US personnel will be pulled out”
“Oh, and by the way I insist you re-pay the US for all the aid we have delivered since the beginning of WW2”
Also “We will deny any form of assistance to any nation that does business with the EU”
Speak loudly and wield a huge stick.
That would not scare them, I do not think. They are very strong ideologues. Better to make them question what they claim their “values” to be, and speak the truth on issues that they do not let their people hear.