If they block Norwegian, then as a retaliation, the EU will Finally stop the UPS and FEDEX flights intra-EU with US crewed N-registered aircraft.
Although our US friends claim that this is not cabotage, the EU does consider flights within the EU as cabotage as it is one economic region. This has been allowed so-far, but if Trump wants to play the protectionist game, it will have grave consequences for Fedex and UPS.