The bigger question, of course, is what price American voters are willing to pay for accepting these new rules. Here’s one possible consequence: If it becomes clear that the United States no longer supports NATO’s security guarantee — or supports it for some countries and not others — then does the alliance have any value at all? Maybe the whole thing comes crashing down, NATO becomes worthless, and the United States finds itself all alone at the poker table. Without its European bases, the United States ceases to be a force in Eurasia. The U.S. military will have trouble projecting military power into the Middle East or Africa. Perhaps Russia, or China replaces the United States as the dominant power, particularly if the E.U. collapses — and then they set the trading rules. Is that what we want?

The other risk is that the coming trade wars take a toll, and not just on Harley-Davidson. U.S. multinationals are by far the biggest beneficiaries of the trade arrangements around the world. If American markets are no longer open to European companies, then why should Europe be open to Amazon, Facebook and General Motors? Europeans might decide to impose new tariffs and taxes — or use antitrust legislation to try to break up big American corporations.