Mr. Trump’s suggestion that it is “impossible” for American farmers to sell their products to the European Union is wrong. In fact, the 28 countries of the European Union are the United States’ fifth-largest export market for agricultural goods, like tree nuts and soybeans, totaling $11.5 billion in 2017, according to the Department of Agriculture.But the United States did import about $10 billion more in agricultural products, like wine, beer and chocolate, from the European Union than it exported there. (Overall, the United States has had an agricultural trade surplus with the rest of the world since 1960.) The European Union does impose a higher average tariff on agricultural products (11 to 12 percent) than the United States (about 5 percent), but about a third of farm goods enter both the European Union and the United States tariff-free, according to the World Trade Organization.