Durham, N.H. — The United States has long taken its northern neighbor for granted. To the man on the street, Canada is most often perceived as a friendly country within the US sphere of influence. It shares the world's longest unguarded frontier, sports a maple leaf on its flag, and produces fine hockey players. Canada has even been referred to as the 51st state.
But unless that perception changes, and unless differences over specific political, economic, and environmental issues are resolved, the US-Canada bond may be seriously damaged, according to analysts of US-Canadian relations.
The relationship between the United States and Canada is in such a state of deterioration that there may be ''resulting harm to the interest of both peoples if such deterioration is allowed to continue,'' warns Kenneth M. Curtis, former governor of Maine and ambassador to Canada under President Carter, and John E. Carrol, a specialist in Canadian-US environmental relations at the University of New Hampshire.
The solution, Dr. Carroll and Mr. Curtis suggest, is a new Canada policy in Washington that would carefully look at US-Canadian conflicts and deal with them before they become major issues.
In a book recently released in Washington - ''Canadian-American Relations: The Promise and the Challenge'' - Carroll and Curtis argue that despite the efforts of Canadian government outreach programs over the past few years, Americans ''still know very little fact and have even less insight into this highly sophisticated and globally conscious society north of the border. While some isolationists might argue that ignorance is bliss, this state of affairs is undesirable and insulting at best, costly or even dangerous at worst. It is in the national interests of both peoples that the American people develop a greater and more insightful knowledge of their fellow North Americans.''
In economic terms, few US citizens realize that Canada and the US are each other's largest and most important trading partners. Canadian exports to the US in the early 1980s reached $45 billion. US exports to Canada were worth $47 billion. Such is the interdependence that Canada invariably follows every fluctuation in the American economy - except that hard times for the US are often even harder for Canada. And recent US calls for protectionist trade policies curry little favor in Canada, experts point out.
Politically, even fewer Americans acknowledge that the close relations and economic integration enjoyed by the two countries between World War II and the early 1960s have not carried through into the '80s.
Canada did not support US involvement in Vietnam, and more recently, has had little sympathy for US foreign policy in Latin America - specifically El Salvador. The Canadian government is equally displeased with the lack of US consultation about, and subsequent military intervention in, Grenada, a Commonwealth ally.
There is also little American tolerance - especially under the present administration - for the social democracy of Canada's Liberal governments during the past decade, Dr. Carroll says.
At the same time, increasingly serious environmental conflicts closer to home , such as acid rain, use of the Great Lakes, fishing rights, and energy use, have strained bilateral relations.
In an interview at the University of New Hampshire, Dr. Carroll says if this doesn't happen, Canadians will be faced with a dilemma: ''Do they want a high standard of living and at the same time surrender economic and polictical decisionmaking to Wall Street and Washington; or do they want to make their own decisions and take less. The question is: Just how much willingness is there to suffer economic sacrifice?''
Judging from the example of Quebec, Dr. Carroll says, Canadians may be willing to go just far enough to make a point.
Carroll and Curtis see their new Canada policy as alternative to such a state of strained relations. The policy would include:
* A high-priority presidential commitment to US-Canada relations.
* A deputy assistant secretary of state for Canadian affairs as well as an deputy assistant secretary of state for Mexican affairs. (As the authors' work was going to press, the Reagan administration was appointing James M. Medas to the Canadian affairs post.)
* The creation of formal and informal institutions or commissions, governed by rules of procedure to deal with the day-to-day problems.
* Encouragement and support to subnational government to develop Canadian expertise.
If a new US-Canada initiative is not undertaken, the authors warn that ''North Americans in the broadest sense would be the losers, as would be those nations who look to the United States and Canada for leadership in human rights, democratic ideals, and - of growing importance - the supply of food and assistance to those in need.
''Canadian-American amity,'' they continue, ''has global significance, both in terms of stability and peace and also in terms of what these two nations can accomplish in their joint compassion for the deprived peoples of the developing world.''
Both countries must realize, Dr. Carroll says, ''that the long-term best interests of Canada are also the long-term best interests of the US. But they also must realize that short-term best interests differ.''
An incomplete version of this story ran Nov. 2.m