WASHINGTON — David Wilkins will be sworn in today as ambassador to a country many Americans consider the United States’ best friend.

Canada and the United States share the world’s largest unguarded border. Their people speak the same language. Foreigners often can’t tell an American and a Canadian apart.

But Canada hasn’t felt too friendly toward the United States lately.

As U.S. ambassador to Canada, Wilkins, who steps down after 11 years as speaker of the S.C. House, will face widespread Canadian discontent.

It is a degree of tension, according to Canadians, that has escalated beyond their usual complaint that Americans think of their country as the 51st state.

The most recent problem began when President Bush took office in 2001 and decided to forego the traditional first trip abroad to Canada — visiting Mexico instead and then not setting foot in Canada until November 2004.

“He has taken the Canadians for granted and continued to take the Canadians for granted and for some reason the Canadians don’t like that,” says Ivo Daalder, an international relations scholar at Washington’s Brookings Institution.

There are more concrete issues over which the two countries have clashed in recent years:

• Iraq — The Canadian government, supported by its citizens, strongly opposed U.S. intervention in Iraq.

• Missile defense — Canada angered the Bush administration this year by refusing to participate in the construction of a missile shield to protect the U.S. and some allies from a nuclear attack.

• Lumber — Canadians resent that the U.S., despite free-trade agreements, heavily taxes their softwood lumber — a major Canadian industry. The U.S. accuses Canada of unfairly subsidizing softwood.

• Beef — Canadians are angry about a continuing U.S. ban on the importation of Canadian cattle after a 2003 mad cow disease scare.

Added to the perceived arrogance of the United States on military and trade issues and the resentment toward Bush, there is Wilkins’ predecessor, Paul Cellucci.

“He wasn’t liked a lot,” says Guy Taillefer, an international affairs reporter for the Montreal daily newspaper Le Devoir. “We are hoping the new ambassador won’t be as intervening in Canadian affairs.”

Cellucci, upon taking up residence in the Canadian capital, earned a reputation for brusqueness and a certain lack of respect for the Canadian point of view — on everything from their opposition to the war to their steps to legalize marijuana.

Just as Wilkins led Bush’s presidential campaign in South Carolina, former Massachusetts Gov. Cellucci directed it in his home state.

But if Cellucci didn’t mince words when angry with Canada, Canadians didn’t hold back either.

Perhaps the most infamous of the cross-border insults was that uttered in 2002 by a spokesman for then-Prime Minister Jean Chretien, who responded to a reporter’s question about Bush and Iraq by exclaiming, “What a moron!”

Since then, tempers have cooled considerably, says another Canadian who keeps a careful eye on U.S.-Canadian relations.

“You have to look beyond some of the problems we’ve had recently,” says Douglas Goold, president and CEO of the Canadian Institute of International Affairs. “They’re not the sort of problems that have changed the relationship fundamentally,”

Yes, Canada and the U.S. have disagreed on Iraq. But they also disagreed on the war in Vietnam and remained close allies.

Goold wants Americans to know that Canadian soldiers have played important combat and peacekeeping roles in Afghanistan, and that Canada has contributed $350 million to the reconstruction of Iraq.

Janet Hiebert, a political studies professor at Queen’s University in Ontario, says that while Bush is still unpopular in Canada, his relationship with current Prime Minister Paul Martin is far better than his relationship with Chretien — though both Martin and Chretien are members of Canada’s Liberal Party.

She has some advice for Wilkins, should he want to avoid the pitfalls of his predecessors.

Realize, she says, that Canadians, while similar to Americans, are not the same — and respect those differences.

“We’re not as driven by religion; we are not as afraid of ‘the state.’ We are much more egalitarian. We do not have private universities. We’re much more humble.”

And, perhaps because Canadians are so humble, Hiebert can acknowledge:

“We have a little chip on our shoulder.”

Reach Markoe at (202) 383-6023 or lmarkoe@krwashington.com