Calling the European Union "very difficult to deal with," President Donald Trump said Friday the United States would move to enact a 50% tariff on the EU.

U.S. companies are also still cautioning about how tariffs could affect their businesses. On Walmart 's ( WMT -1.35%) earnings call last week, CEO Doug McMillon warned about potential repercussions. President Trump responded on social media that Walmart makes billions of dollars in sales, and that it should "eat the tariffs." But can it?