Sniper at St. Patrick's Day street party in Waterloo, Ont., a tactical officer who was part of emergency plan

WASHINGTON, D.C. — Canadians’ affection for the United States tends to rise and fall with whoever’s in the White House. It dropped for president George W. Bush, rose for Barack Obama, and then plunged during Donald Trump’s first term, only to rise again with Joe Biden. In the first year of Trump’s second presidency, however, Canada’s fondness for its southern neighbour has plumbed new lows. Also new is that Americans’ views of Canadians have also made a historic shift — for the worse. According...