In the Haskell Free Library and Opera House, you can watch a show with one foot in Canada and the other in the United States. Built at the turn of the last century, when both countries boasted about the world’s longest undefended border, the cultural centre was created for Derby Line, Vermont, and Stanstead, Quebec. Nancy Rumery, the librarian, says the towns were a “single community that just happened to have an imaginary line drawn through it.”

After September 2001 however, America started making changes. You can still park in Canada and walk across the border to the front door. But now American officials watch to make sure you go back the same way. Elsewhere in the twin towns, movement has been curbed. Although Derby Line and Stanstead share water and sewerage systems and a Rotary Club, they are no longer one community.

Many locals hesitate to cross the border to shop, worship or see friends for fear of being detained and fined. The attack in Ottawa last month by a lone gunman, who killed a Canadian soldier and stormed parliament, will most likely make matters worse.

After meeting his Canadian counterpart in Ottawa in the wake of the attacks, John Kerry, the United States secretary of state, was firm about the need to tighten security. It is debatable whether more security on what Senator John McCain recently called the “porous” northern border really will make Americans much safer from terrorism. But it seems hard for politicians to shake off the habit of Canada-bashing. Both Mr. McCain and Hillary Clinton (in 2004) have stated, wrongly, that the 9/11 terrorists entered American territory through Canada.

Most certainly, these “tweaks and changes” will affect economic exchanges between two countries who are each other’s’ largest trading partners. Increasing amounts of security will also further fray social relations between once-friendly neighbours. Illegal immigration, which haunts American relations with Mexico, is less of a concern in Canada’s case. Of the 420,789 people apprehended by America’s border patrol in 2013, 98% were caught on the country’s south-western edge. On the northern side, guns and drugs are the main cause of concern.

However, policing a line which runs through remote spots like the hills of Montana and Alberta and four Great Lakes is no easy task. Since 2001, America has increased its border agents looking at Canada from 340 to 2,200. It has also added aircraft with sensor arrays, thermal cameras, video surveillance and unmanned aircrafts to watch remoter areas.

Canada has addressed some American concerns by arming 5,685 customs officers, agreeing to joint patrols on the Great Lakes; and by forming teams that include coast guards, border agencies and police from both countries. All of these changes have cost Canada an additional C$92 billion ($77 billion) on security since 2001.

Source: The Economist