It’s not a bad idea to challenge the assumptions underlying United States policies. It helps ensure that policymakers continue to promote US interests.

But on the question of whether the European Union’s existence is in US interests, a recently published paper from the Strategic Studies Institute of the US Army War College says “the evidence is consistently clear.”

Undermining the EU—by backing Brexit or suggesting other EU countries follow the UK out of the union—”risks the further unraveling of the international order that is central to American prosperity and security,” the paper said.

The document makes the case both for security policy as well as economic and trade policy.

To summarize the security aspects, European integration has prevented another war on the continent that saw massive bloodletting twice in the span of 25 years during the first half of the twentieth century.

On the economic front, the collapse of the EU would jeopardize European economic strength. “While one might think the demise of a major economic competitor would benefit the United States,” the paper argues, “the end of the euro alone would have catastrophic effects on the American economy, worse than the recent Great Recession.”

The US and European economies have become so interwoven that the end of the EU “would deal a body blow to transatlantic trade and investment.” The EU is now the US’s biggest trading partner, accounting for 20 percent of all US trade, far surpassing and, China, Mexico, and Japan. The economic relationship between the USand the EU generates trade flows in goods and services of billions of dollars per day. Machinery and transportation equipment are the most traded products between the two and trade in chemicals, fossil fuels, medical products, pharmaceuticals, power-generating equipment, scientific equipment, automobiles, beverages, and food is also robust.

“It is naïve to assume,” the paper emphasized, “that if the EU were to fall apart, today’s transatlantic trade and investment patterns would simply disaggregate into disparate bilateral trade partnerships between the United States and each of the EU member states. In this case, the whole really is greater than the sum of the parts.”

More likely what would happen, the report concluded, would be “massive economic dislocation characterized by capital flight from Europe and widespread unemployment, leading ultimately to a reduction of transatlantic trade and investment, a seizure within global capital markets, and a loss of American jobs.”