Leaders of the Group of Seven rich nations headed for a summit in Canada on Thursday. According to Reuters, the leaders are more divided than at any time in the group’s 42-year history. U.S. President Donald Trump’s “America First” policies risk causing a global trade war and deep diplomatic schisms. As a means of rebuilding American industries, Trump has imposed hefty tariffs on steel and aluminum imports, including those from key G7 allies like Canada, Japan and the European Union.