Few people have watched the arc of Canada-US politics as closely as Caroline Mulroney. The daughter of former prime minister Brian Mulroney, she grew up around a cross-border relationship shaped in part by her father’s bond with Ronald Reagan — a partnership that helped produce a landmark Canada-US free trade agreement and set the tone for decades of co-operation. "It was his work with Ronald Reagan that led to our first free trade agreement with the United States, built on their friendship and the belief that our economies…