The U.S.-Canada trade war escalated Tuesday after Prime Minister Mark Carney announced new Canadian tariffs on some $20 billion in U.S. goods. Canada will double its tariff rate on U.S. steel and aluminum to 50%, matching Mr. Trump’s rate. Multiple press reports said a proposed agreement to avert a 50% U.S. tariff on $20 billion in Canadian goods broke down last week, partly because of objections from U.S. steel and aluminum lobbies. The mooted deal would have lowered U.S. tariffs on Canadian steel and aluminum to 25% from 50%.