Editor’s Note: Guy Verhofstadt, a former Belgian Prime Minister, is president of the Alliance of Liberals and Democrats for Europe Group in the European Parliament. The opinions in this article are those of the author.

CNN  — 

Since the end of the World War II, Western nations have shared the belief that international trade was a virtue. While progress has too often been lethargic, in the decades since, the United States and European nations have worked together to reduce barriers to trade.

This went hand in hand with a special bond between our two continents – culturally, militarily, as a broad alliance of free nations.

Together, progress has been achieved in the form of the institutions such as the World Trade Organization and the European Community – the forerunner to the European Union.

Trade-based agreements between the EU and the United States multiplied. Progress was made toward a comprehensive US-EU trade deal. Perhaps under a different president, these talks could even have been concluded. By signing trade deals with Japan and Canada, the EU has shown it is capable of cutting global trade deals and furthering rules-based trade.

As US companies have invested in Europe, successful European companies – for example, automakers – invested in the United States.

BMW, a legendary German carmaker, employs thousands of workers at its biggest production plant in South Carolina, which builds nearly half a million vehicles a year. Many of these are exported to Europe and elsewhere.

As with so many policy areas, the election of Donald Trump – an isolationist and protectionist – has upended the status quo. In the capitals of Europe, the trans-Atlantic relationship is turning into a nightmare.

German Chancellor Angela Merkel rightly expressed exasperation at the Trump administration’s suggestion that European cars are a threat to US national security, calling it a “shock.” This was German understatement.

Trump believes the United States “loses” when it runs trade deficits with other countries. Confusingly for many Europeans, traditionally free-trading Republicans appear to go along with Trump’s 16th-century view of international trade.

Following European Commission President Jean-Claude Juncker’s negotiations with Trump in July, the EU made a number of concessions by committing to importing more liquefied natural gas, soybeans and other products from the United States.