It was good to note the cordial meeting last week between President Reagan and Prime Minister Trudeau. Whereas relations between the United States and Canada are generally good, there have been several challenges in recent years - primarily over acid rain and trade.
Just how far the Washington conversation advanced Mr. Trudeau's two-month-old peace initiative is hard to gauge. Certainly it is a worthy effort on his part; thus far he has met with leaders of several nations, trying to gain their support.
At least two levels of stalemate over nuclear weaponry appear to exist at the moment: between the United States and the Soviet Union on the several parleys dealing with nuclear arms control, and between Western European governments and peace movements in their countries, which have gained renewed vigor over the past two years.
Sometimes third parties can bring movement to stalemate by providing a face-saving approach that permits negotiation to begin moving forward. It may be that Mr. Trudeau and his peace initiative will ultimately fill that role.
In any case, worthy of support is his aim of ''changing the trend line'' so that the world is moving toward peace rather than in the direction of increased tension. Open to question, however, is whether Mr. Trudeau's proposed summit of leaders of the five nuclear nations would be helpful at this time. It might result in an easing of tensions or possibly even a breakthrough toward agreement on nuclear arms control.
However, it might have a negative effect by raising unrealistic hopes, only to dash them if no agreement is produced. It has been the position of several American presidents, including Mr. Reagan, that summit meetings between potential adversaries ought not to be held unless there is sufficient preparatory staff work to indicate that prospects for success are reasonably good. President Reagan wished Mr. Trudeau ''Godspeed in your efforts to help build a durable peace,'' but did not comment on the summit proposal, which the Canadian leader considers a key to his plan.
The Reagan-Trudeau meeting may have been helpful in keeping relationships very friendly between the two nations, which are each other's largest trading partners. But on several issues Canada seeks more than words. Two of the most important: diminution of air pollution from the US Midwest, which Canadians believe is heavily responsible for acid rain in eastern Canada, and a decrease in US protectionist proposals which would harm Canadian exports.