THE U.S. & CANADA: Family Feud.

• Author: Smith, Patricia
• Position: INTERNATIONAL - Chronology

The two nations are so close it's sometimes hard to tell them apart. But recent disputes have caused fractures in this critical alliance.

The United States and Canada share the longest border in the world. For most of our history, that 5,525-mile boundary was pretty much ignored by people on both sides, who crossed back and forth as they liked. There are even homes, businesses, and public buildings like libraries that have rooms on both sides of the divide.

Today, there are at least 70 energy pipelines that cross the border. Our phone systems are so integrated that you can't even tell that you're making an international call. More Americans live in Canada than in any other foreign country, and more Canadians travel to the U.S. than visitors from any other nation.

"Canada is the country that most resembles the United States," says Robert Bothwell, a professor of Canadian history at the University of Toronto. "We share the same cultural outlook, the same foundations to our culture, and that's really been true since the 18th century."

Long History of Partnership

Despite our long-standing common interests and broad similarities, relations between the two countries have become increasingly tense over the past year. Seeing some Canadian policies and treaties with Canada as impediments to America's success, President Trump imposed steep tariffs on key Canadian exports to the U.S. and threatened to rip up an important free-trade deal. He also hurled insults at Canadian Prime Minister Justin Trudeau, who didn't see things his way.

Trump has dealt with Canada "in a way that no U.S. president has ever done," Bothwell says.

The two nations have a long history of close partnership (see key dates, p. 12). Canada has been one of America's closest military allies; it fought alongside the U.S. in both world wars, the Korean War, and the Gulf War. Both countries have long traditions of taking in immigrants. There's been a free-trade agreement between the two nations for decades, and Canada is the biggest importer of American goods.

"This is the oldest and deepest relationship that the United States has," says Janice Stein, the founding director of the University of Toronto's Munk School of Global Affairs.

The recent tensions first flared during the 2016 presidential election. As a candidate, Trump called the North American Free Trade Agreement (NAFTA)--the 1993 deal between the U.S., Mexico, and Canada--the "worst trade deal ever" and vowed to renegotiate the pact or pull out of it altogether.

'Sorry State of Affairs'

Trump won a lot of support on the campaign trail by talking about how bad NAFTA had been for American workers, who...