Trump decided that the trade war with the EU needed some further escalation. It does not really amount to much in the grand scheme of GDPs involved, but it is going to hit the more rural areas in Europe. Part is an old heritage of the Boeing-Airbus global competition. If the WTO would grant victory in that mutual government aid quarrel, it perhaps does not happen. But yeah... beating the drums is what Trump likes to do. There is a big cheese mountain as well in the US, but I guess Trump just likes to retalliate on typical symbolic European gourmet stuff.