[Castlebar]

The reasons were outlined in James Madison's letter to congress; the declaration was the answer form Congress.

No where in the Madison Letter, or in the transcripts of congressional debate on te declaration, is there any stated war aim abut annexing all or part of Canada. Private citizens in various roles stated desires along those lines, but the idea that the U.S. went to war to seize Canada has more to do with the anglophile bias of historians and professors that with reality.

[BroJoeK]

Castlebar: "...the idea that the U.S. went to war to seize Canada has more to do with the anglophile bias of historians and professors that with reality."

I'd call it simple common sense, since:

1. In 1775, among its first actions, Congress sent two separate expeditions (Montgomery & Arnold) to conquer Canada.

2. Those invasions failed, but that did not stop Benjamin Franklin from demanding Quebec during the 1783 Paris peace negotiations.
   He didn't get Quebec, but did get Ohio.

3. Less than a month after declaring war on Britain in June 1812, the United States under General William Hull again invaded Canada, at Detroit.
   Hull was promptly defeated.

4. In October 1812, the US under Major General Stephen Van Rensselaer again invaded Candad, at Niagara.
   Van Rensseler was defeated at Queenston Heights.

5. These two invasions were intended as parts of a four -pronged invasion, the third being Major General John Dearborn's advance to Montreal.
   Dearborn was defeated at Lacolle, Quebec.

6. In the spring of 1813, Americans again invaded Canada -- three different times -- burning Parliament buildings in Toronto, capturing Fort George on the Niagara River and finally suffering defeat at the Battle of Beaver Dam.

7. In the fall of 1813 the US three more times invaded Canada, first under General (future President) William Henry Harrison.
   Harrison's victory at the Battle of the Thames (near Chatham, Ontario) helped eventually elect him President, but his army's enlistments expiring forced them to soon retreat back to Detroit.

8. In October - November 1813, the US twice more invaded Canada, along the St. Lawrence River -- US Major General Wade Hampton marched north from Lake Champlain to join a second force under General James Wilkinson, planned to embark in boats and sail from Sackett's Harbor on Lake Ontario, to capture Montreal.
   Hampton was defeated at Chateaugua (near Ormstown, Ontario), Wilkinson was defeated at Crysler's Field (Cornwall, Ontario)

By my count, that's eleven different invasions of Canada between 1775 and 1813, plus Franklin's 1783 attempt to negotiate acquisition.
So I'd say some dreams of conquest take a long time to die.