But the outlook for the European economy will come a close second. Already in a long-term funk, Europe’s clapped-out economic engine leaves it even more exposed to a dose of Trumpism than in 2016. At the start of the week—as long ago as it may seem—the focus in EU circles was on a “new and comprehensive horizontal strategy” for its flailing economy.

The EU is seeking to accelerate talks with the UK on a new defense and security pact, with the election of Donald Trump raising concerns in Europe that it will need to boost aid to Ukraine amid the possibility of reduced American support. A UK-European ...